Probably no laws of physics have been so over invoked and less understood than the laws of thermodynamics. Everyone it seems is using the laws of thermodynamics to justify every position imaginable in the field of weight loss.

Journalists often throw out the laws of thermodynamics to prove or disprove dietary regimens they’re writing about. Authors of various blogs and other online sites rabbit on about how the laws of thermodynamics are aligned with their pet theories.

And even worse, research scientists – who really should know better – more often than not misquote the laws of thermodynamics, especially when talking about the possibility of a dietary metabolic advantage. ‘It can’t be valid,’ they sniff, ‘it violates the laws of thermodynamics.’

So, I figured is was time to delve into these mysterious laws so that readers of this blog at least can know thermodynamic nonsense when they see it.

When you get a grasp of the laws of thermodynamics it becomes pretty easy to see how they can be confusing not only to the great unwashed masses but even to scientists who have never really taken the time to study them. Thermodynamics are seemingly simple at first glance, but the more you dig into them, the more complex they become.

To see what I mean, take a look at the syllabus for the thermodynamics course at MIT and skim through a few of the lectures.

Before we jump into these laws, I want to show you why scientists typically heap scorn on anyone who claims to have somehow violated the laws of thermodynamics.
The author of a book of thermodynamics that I have writes the following:

No violation of any law of thermodynamics is known to have occurred in over 200 years of research in this area.

Most physicists consider the Second Law of Thermodynamics the most universal ‘governor’ of natural activity that has ever been revealed by scientific study.

Sir Arthur Eddington wrote in 1915

If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

And Ivan Bazarov wrote the following in a thermodynamics text from 1964:

The second law of thermodynamics is, without a doubt, one of the most perfect laws in physics. Any reproducible violation of it, however small, would bring the discoverer great riches as well as a trip to Stockholm. The world’s energy problems would be solved at one stroke. It is not possible to find any other law (except, perhaps, for super selection rules such as charge conservation) for which a proposed violation would bring more skepticism than this one. Not even Maxwell’s laws of electricity or Newton’s law of gravitation are so sacrosanct, for each has measurable corrections coming from quantum effects or general relativity. The law has caught the attention of poets and philosophers and has been called the greatest scientific achievement of the nineteenth century.

Now that you somewhat understand the strong feelings of those in the know about thermodynamics, you can see why they would disparage anyone purporting to break or repeal these laws. And it helps to understand the vituperation heaped on Robert Atkins who wrote one of the most hubristic and outright ignorant statements imaginable showing a total lack of understanding of the laws of thermodynamics when he said:

When I make this claim, that you can lose more weight on a higher number of calories, I seem to be breaking the law—one of the hallowed laws of thermodynamics. Many powers-that-be get terribly provoked when I repeal their laws. But the calorie theory is a false law that is meant to be broken, and ketosis/lipolysis is the instrument for breaking it.

As reported in Gary Taubes Good Calories, Bad Calories, this comment and others like it may have lead John Yudkin to say of Atkins’ book that its “chief consequence [may have been] to antagonize the medical and nutritional establishment.”

But, since Atkins wasn’t really a physicist, it’s easy to see how he could have become confused.

There are four laws of thermodynamics, but we’re going to concern ourselves in this post only with the first and second laws. The other two laws – the zeroth law and the fourth law involve temperature, are highly theoretical, and aren’t really relevant to the discussion at hand.

The first law of thermodynamics is the conservation of energy law and states that energy can neither be created nor destroyed. Another way of stating this law is to say that the energy of a system plus surroundings is constant in time. This first law is where the mistaken idea that ‘a calorie is a calorie’ that misguided people always want to parrot comes from. And on the surface it seems to make sense.

If energy can’t be created or destroyed why wouldn’t a calorie always be a calorie? That’s where the second law comes in.

The second law of thermodynamics says that the entropy of the universe increases during any spontaneous process. What this means is that it is impossible for a system to turn a given amount of energy into an equivalent amount of work. It is this second law that is really the ‘a calorie is a calorie’ law, and, in fact, the second law shows, in terms of weight loss at least, that a calorie isn’t necessarily a calorie.

These two laws of thermodynamics can be summed up cleverly. The first law says you can’t get something for nothing, and the second law tells you that you can’t break even.

Since it’s the second law that applies to living, breathing animals, and since it is the one most often confused in the calorie issue, let’s look at it a little more closely. The second law is the law driving chemical reactions, and since we’re nothing but a bunch of walking chemical reactions it is the one that applies most to us.

The second law is a dissipation law in that it says that in any reaction that is irreversible (most of the chemical reactions that give us life) there is a loss or dissipation of energy in that reaction. If substance A converts to substance B via a chemical reaction in the body, then substance B has a lower energy than substance A. In other words energy is lost to the universe in that reaction. There is no reaction that doesn’t end up without a loss of some energy to the universe. This loss of energy is called entropy.

The second law can kind of be summed with this equation:

calories in = calories out + entropy

If we substitute numbers in the above equation it could look like this:

100 calories in = 70 calories out + entropy

If we solve this equation for entropy, we can see that entropy is 30 calories. Or, in this case, 30 calories of energy are lost.

The larger the number for entropy, the more inefficient the system is, i.e., more energy lost from the system forever.

For example, when you drive a car only about 10-12 percent of the energy contained in the gasoline actually is converted to the work of propelling the car – the rest is lost to heat (entropy). This irretrievable loss is the reason a perpetual motion machine can never be built although many have tried. No matter how efficiently such a machine might be designed it will ultimately run down because of these little energy (entropy) leaks here and there. (I’ve used entropy as if it is synonymous with energy when in technical terms it really isn’t, but it’s easier to think of it that way.)

How does this apply to weight loss?

Each of the many chemical reactions in the body end up dissipating energy. We get our energy in the form of calories from the food we eat. This energy gets consumed in all the countless chemical reactions that go on all the time. Just like an automobile, we are not all that efficient. We don’t convert calories to energy on a one to one basis because of the loss of energy to the universe described by the second law.

This is all basic stuff, but it gets interesting when we start to look at how the different macronutrients (fat, protein and carbohydrate) affect the process.

As I’ve discussed in this blog frequently, we need to maintain our blood sugar in a fairly narrow range.

We need blood sugar to supply energy to certain cells that can’t use it in any other form (the red blood cells, some brain cells and others). We can get plenty of sugar into our blood and have no trouble keeping our blood sugar up if we eat carbohydrates. The carbohydrate-containing foods get broken down into their sugar molecules that are then absorbed from the intestines directly into the blood. In our high carb world our problem isn’t too little sugar but too much. But in the early years of our existence on the planet it wasn’t like this. We didn’t have access to the bounty of easily absorbed carbs that we do today, yet we still had the need for sugar in our blood. As a consequence we evolved mechanisms to convert other nutrients – primarily protein – into sugar.

If we have a diet containing plenty of carbohydrate, the carbohydrate goes into the blood as sugar.

There are very few chemical reactions along the way, and there is a loss of energy to the universe with each of these reactions. But, since there aren’t many conversions, there isn’t a lot of energy loss.

If we have no carbohydrates (or few) in the diet, however, it’s a different story. In order to maintain the necessary sugar level in the blood the body is forced to make sugar out of protein, which isn’t a simple operation. Look in any basic biochemistry textbook and you can see all the reactions required to convert protein to sugar, and each one of these reactions consumes energy just to take place but loses energy to the universe in the process as well. It’s much less efficient for the body to convert protein to sugar than it is to simply take the sugar as it comes in already formed.

The second law of thermodynamics virtually mandates that there be a larger loss of energy when one has to convert protein to sugar instead of merely using the sugar as it comes in. Since there are 4 kcal of energy in a gram of sugar and 4 kcal of energy in a gram of protein, it should be apparent that less of the 4 kcal in a gram of sugar will be dissipated than will be the 4 kcal in a gram of protein if this gram of protein has to first be converted to sugar.

And, consequently, one would think that a diet low in carbohydrate and higher in protein and fat (both of which have to be converted to sugar) would bring about a greater weight loss than a diet of the same number of calories but with higher levels of carbohydrate. In fact, the second law of thermodynamics predicts this very phenomenon. But despite this rather obvious notion that complies perfectly with the second law, many ignorant people continue to cling to the idea that ‘a calorie is a calorie’ despite that idea flying in the face of the second law. I suppose these people discount the second law. If so, then they should spend their time putting together a perpetual motion machine, which, if they could, would garner them a lot more fame than their inane posturing on the inevitability of the second law might do.

A classic example of how the second law works is in the difference between regular and premium gasoline. Both regular and premium have the same exact number of calories per gallon, but premium burns more efficiently. In other words, the calories contained in the premium gas get ‘wasted’ at a lower percentage in propelling the car along the road than do the calories in the regular. A high-performance automobile designed to squeeze the most out of a gallon of gas will get better mileage on premium than on regular gasoline, yet the calories in are exactly the same.

In the human body this inefficiency can be measured as an increase in metabolic rate and an increase in body heat being produced under laboratory conditions. One would assume that since the second law is inviolable and always in operation that people eating a diet low in carbohydrates and high in protein would produce more heat than those consuming the same number of calories but composed of a much higher percentage of carbohydrates. And that is exactly what is found.

In a paper published in the Journal of the American College of Nutrition researchers examined this effect in ten healthy young women who consumed either a high-protein, low-carbohydrate or a lower-protein, higher-carb diet of the same number of calories. The researchers used these women as their own controls, providing them with the first diet followed by measurements in the lab, then 54 days later with the second diet and lab evaluation.

Precise measurement of heat and metabolic rate showed that when the women followed the high-protein, low-carb diet they produced almost twice as much heat as they did when consuming the higher carb diet of the same calories. In the higher-carb diet the entropy was smaller than in the higher-protein diet, which would be expected from the second law.

As the authors of the paper put it:

These data demonstrate that meal-induced thermogenesis at 2.5 hours post-meal averages about twofold higher on a HP, low fat diet versus a HC, low-fat diet. Generally, postprandial thermogenesis has been associated with the protein content of a meal, and our data confirm this relationship. However, the difference in the energy cost of HP versus HC diets, particularly in the context of weight loss promotion, has not been addressed by healthcare professionals. Increased diet-induced thermogenesis, in association with the preservation of REE [resting energy expenditure], may contribute to the reported weight loss success of diets high in protein with moderate levels of carbohydrate and lends credence to the observation that weight loss on HP diets is predominately body fat, not body water.

Bear all this in mind the next time you tell someone that it is possible to lose more weight on a greater number of calories as long as those calories are low-carb calories, and that someone pooh poohs you with the old ‘That can’t be possible. It violates the laws of thermodynamics. A calorie is after all a calorie.’ Ask them precisely which laws of thermodynamics it violates and ask them to tell you how.

Then sit back and watch the fun.


  1. “HP, low fat diet versus a HC, low-fat diet”
    This is why folks say its not the carb restriction that is responsible. Simply swapping carb for fat while holding protein constant, has not shown the same effect. OTOH, In real life, people who restrict carbs will in general eat more protein. This, to me, is where things get messy, because life isn’t a carefully controlled experiment. While I appreciate the debate for the sake of scientific accuracy, and being a bit of a geek I like reading studies. The question that is often over looked is “SO WHAT?”. Whether there is or isn’t an advantage metabolically, Low carb diets work, and have been proven to work better in free living conditions. Isn’t that really the bottom line?
    Hi Kevin–
    ‘So what’ is probably an appropriate response. The metabolic advantage at best is a couple of hundred calories a day, which isn’t going to bring about massive rapid weight loss. But it does help. I’d much rather have it working for me than not.

    1. you are out of your minds if you think an extra 200 calories a day won’t help. If you train modestly hard for an hour a day, including warm up, with the extra 200, any human would lose a pound of weight per week. That is not only tremendous, as losing more than 2-3 pounds per week isnt healthy, for weightloss, but think of how easy that is to maintain.
      PS if you think 30% protien is high i would disagree. That percentage is not dangerous longterm and if you follow 1 gram per pound a day that is not a high number to achieve.

  2. “The first law says you can’t get something for nothing, and the second law tells you that you can’t break even.”
    Thanks for the lesson; you really have a knack for explaining complex things in simpler terms!
    I’m glad you enjoyed the post.

  3. Great post again Dr. E. You are on a roll. You have added another bolt to my quiver.
    BTW, does it seem to you there is a deafening silence in response to Good Calories, Bad Calories?
    Taubes has built a seamless argument for the carbohydrate theory of disease with skill and impeccable scholarship. He has checked every citation and accounted for every observation. All the conclusions are supported by pithy quotations from the primary investigators. The facts fit the theory.
    Do you suppose he has stunned the opposition? Or are they still looking up all the big words?
    Hi Marilyn–
    The opposition may be still looking up all the big words. The book has just come out, and it usually takes time to get these things going. When Protein Power first came out it took a while to catch on. It was over a year from the publication date before it made the NY Times bestseller list.
    Keep your fingers crossed.

  4. Dr Eades, I have my perpetual motion machine running at 99 percent. Just a few more small adjustments and You and I can take over the world.
    Good. Count me in.

  5. Dr. Mike:
    You simply cannot imagine how much fun I had reading this brilliant post of yours on the indisputable laws of thermodynacis. Really, you can’t.
    Also, I am 2/3’s of the way through Gary Taubes’ amazing book and am working my way to the climax. I can feel it coming and can hardly wait because I know deep down inside what the outcome will be, but hearing someone of Gary’s reputation and intelligence say it will blast me right out of my chair.
    Keep up your good work and don’t succumb to the dark side. Besides, all they can offer you is cookies, even if they are made with oatmeal.
    Hey Hellistile–
    I’m glad you enjoyed the post. I always fight succumbing to the ‘dark’ side, but it isn’t oatmeal cookies that will snare me. If they tempt me with fresh raisin bread though, I could be a goner.

  6. I may be wrong, but are people also miscalculating the fact that you only have to worry about food calories that are absorbed? If someone ate all their calories in 1 meal- and the breakdown was something like 25% protein, 70% fat , and 5% carbs for around a 2500 calorie meal, I’d very highly doubt that the close to 200 grams of fat gets 100% absorbed by the body. If it did, i’d be highly amazed that our bile duct system is that capable (to help breakdown all the fats). Could LCing cause an overload in our fat absorption system- and if it does- is this healthy for the long term – or at least healthy enough on the basis of an absence of disease causing carbs? Once again, interesting post!
    Hi Aaron–
    The GI tract is pretty good at absorbing all the food that travels along it unless there is some kind of malabsorption syndrome going on. The normal GI tract is able to handle the extra fat from a low-carb diet without much of a strain.

  7. Hey Dr. Mike,
    Thanks for such a great post. As a chemical engineer, I have been well schooled in thermodynamics, but I realize most people really haven’t a clue about how it truly works. My long-time fallback explanation about low-carb dieting and thermodynamics has always been this: Imagine you are tending a bonfire. The fire is low and you are cold, so you begin stacking wood on the fire. If you begin stacking wet wood on the fire, the fire does not burn any larger or hotter, no matter how big the pile gets. If the fire is your metabolism, and the wood is your caloric intake, then carbs are akin to wet wood. No matter how much wood you add, you are continuing to suppress the fire, and just creating a stockpile of fuel (fat). Low-carb eating is like using dry wood. When the fire is low, you add more fuel, and it burns hotter and higher until the fuel is expended. No stockpile is created, you don’t get fat. This hasn’t really converted any naysayers, but is has given many civilians an understanding of why calories in does NOT equal calories out.
    Hi Kelly–
    Thanks for the alternative explanation.

  8. Dear Dr. Eades – A question regarding this comment:
    “Precise measurement of heat and metabolic rate showed that when the women followed the high-protein, low-carb diet they produced almost twice as much heat as they did when consuming the higher carb diet of the same calories.”
    Does this mean that the women had a higher than normal body temperature? Did they feel hot more often and sweat more? Also, does a low carb, high protein diet impact female hormone levels and the body’s response to female hormones?
    Thank you for a great article. Lynne
    Hi Lynne–
    The body temperature did go up. Not by huge amounts, but by double the amount that it did with the high-carb diet.
    A low-carb, high-protein diet does impact female (and male) hormones, but not because of a temperature change. The diet improves insulin sensitivity, and when insulin sensitivity is improved many good things happen. One of these good things is that the liver quits making so much sex hormone binding globulin (SHBG), the substance that binds to the sex hormones. When SHBG levels drop, the levels of free (or active) hormones increase, which is usually a good thing.

  9. Great post. I hate that calorie is a calorie line. I used to get that a lot. Even though I eat a lot more, my macro-nutrient ratios have flipped. I would state that I ate a lot more and you know they would just roll their eyes or say “Sure….”
    Seems pretty logical to me though. I guess all these chemical reactions that give us the “metabolic advantage” is what people refer to as gluconeogenesis. Never really thought about how many reactions were needed for this. The fact the temperature difference was double, would that actually make a person feel warmer by raising the body temperature measurably with a normal thermometer?
    We’re talking temperature changes of under a degree, but these changes could be measured with a standard thermometer. And even a half a degree multiplied by the mass of the body can represent a lot of calories lost to heat.

  10. “A classic example of how the second law works is in the difference between regular and premium gasoline. Both regular and premium have the same exact number of calories per gallon, but premium burns more efficiently. In other words, the calories contained in the premium gas get ‘wasted’ at a lower percentage in propelling the car along the road than do the calories in the regular. A high-performance automobile designed to squeeze the most out of a gallon of gas will get better mileage on premium than on regular gasoline, yet the calories in are exactly the same.”
    Premium actually is less “premium” than diesel, but diesel is much more efficient. Premium allows you to retard the spark a bit longer to allow for slightly higher compression at ignition. Diesel doesn’t use a spark and uses the heat of much higher compression to ignite the fuel, turning more of the fuel into energy. Also, alcohol has less energy per gallon than gasoline, yet a higher (more premium) octane. (that’s pretty simplistic, but makes my point)
    Hi Jeff–
    Thanks for the explanation of the diesel/premium/alcohol differences.

  11. Dr. Mike, wonderful job as always!
    Very appreciated ammunition to be used against the oversimplistic “calories in – calories out” crowd.
    Warm Regards,
    Thanks, Alex.

  12. Dr. Eades,
    You have shown great courage in jumping into explanations of the 2nd law. But I have to take issue with your analogy of high and low octane gas, and add to the salient point of heat flow from the body to the environment.
    The difference in efficiency that you attribute to high octane gasoline is (as I understand) actually due to the higher compression ratio of engines that need it. High octane gas is of no benefit in low compression engines, and burns only as efficiently in low compression engines as regular gas. High compression engines need the high octane to prevent spontaneous combustion before the spark, and the higher efficiency of these engines follows from their high compression, not directly from any property of the fuel.
    About heat flow from the body to the environment–I think that warm blooded animals must have mechanisms that regulate how efficiently their body heat (from all those reactions you describe) get sent to the environment. Such an animal at rest in an environment with a changing temperature could just increase or decrease the rate at which fuel is burned to keep a constant body temperature, but an animal working hard to live cannot just burn less fuel to prevent over-heating. I would presume that they have mechanism like moving blood circulation out to the skin to dissipate heat more effectively, and humans of course use the heat to evaporate sweat, which lowers temperature. I guess what I’m trying to say is that the 2nd law works at multiple levels–the efficiency of the microscopic chemical reactions, and at the macroscopic level as well–how any excess heat is shunted to the environment by macroscopic mechanisms. So this is another way of saying that under some conditions (lots of fat and protein) more calories in can cause even more calories out, consistent with both the first and second laws of thermodynamics.
    Thanks for the chance to express these ideas–
    Hi Art–
    I knew the would be a purist lurking out there on the high-octane gasoline issue.
    You’re right in your description of the various ways in which heat can be dissipated. The second law works at all levels in the various metabolic processes.

  13. The other thing that people forget is that the laws of thermodynamics apply to closed systems. Most of us aren’t closed systems. At least I’m not.
    The first law does, but not the second, which is why the second law of thermodynamics does apply to us.

  14. Nice work once again, doc! Another perspicuous explanation that lit the light bulb for explaining caloric disparity. As a chemical engineer, I was giddy to learn the application of the 2nd law to metabolism, and it all makes perfect sense after thinking through the processes involved.
    Now, I’m not quiet as sold on your gasoline analogy, but I’ll let it slide…
    Thanks again, for putting all of this down in a blog. It’s great that you make the effort to explain and educate.
    Geez. Yet another comment about my not-so-brilliant use of the gasoline analogy. I’m glad you at least enjoyed the rest.

  15. Doesn’t a high-protein diet have other problems? Like higher cholesterol in blood and increased work in the kidneys?
    Uh, no. Read a few other posts in this blog and you’ll see why.

  16. So do I understand correctly–we LOSE thermogenic expenditure if tissues need immediate nutrients (as described by the post-fasting breakfast response)–would this justify the old chestnut to eat small, frequent meals? This is the reason for the higher thermogenic response at night? If a person fasted during the day would this thermogenic response be impeded?
    I’d also want to see the raw data to see if there was a wide range of thermogenesis from patient too patient. I found this:
    … which cites an impaired post-prandial thermogenesis in obese patients. You think overweight people are less entropic, so to speak? Or at least some overweight people?
    The question is how to encourage post-prandial thermogenesis–building muscle through resistance training, yes? Small, frequent meals to keep tissues “fed” or am I misreading this information?
    Hi Jennifer–
    You’ve got to be careful reading too much into these papers. This specific one used a 95% fat diet, but the entire diet was only 50% of the calories required to maintain REE. Anyone would decrease thermogenesis with calories cut in half.
    You don’t have to increase post-prandial thermogenesis; it increase all by itself with almost any diet as the body works to partition the nutrients. The question is what increases it the most? And the answer is: protein.

  17. i have been having a noticeable thermic effect after high fat meals (my diet is very low carb, moderate protein, high saturated fat). sometimes the effect is so pronouced i have to turn on the air or drink ice water to cool off. after reading your report, i’m still unclear as to how the fat causes a thermic effect. are you saying my body has to work harder to process it -the heat then being a side product of digestion of a high fat meal? if ancient man had a mostly meat/fat diet, how would this thermic effect be beneficial? you would think they would adapt to have a low carb diet be most efficient and energy sparing. weight loss aside, is it necessarily a good thing to crank up one’s metabolic rate. wouldn’t a lower metabolic rate be better for longevity? i should note, i do not get this effect when i eat protein or carbs. my main fats are red meat, butter, coconut oil.
    Hi susan–
    Fat can cause a thermic effect, but in a different way than does protein. It has to do with futile cycling (reactions that take place producing heat but producing no product). These can be activated with a high fat diet, which can also increase the number of mitochondria and increase the number of uncoupling proteins and the leaking of protons across the inner mitochondrial membrane – all events that increase fat burning without increasing any actual work done.

  18. Dr. Eades, this post may be my favorite of all that I have read since I found your blog!
    In the immortal words of Harrison Ford in Mosquito Coast: “It’s not magic; it’s thermodynamics!” 🙂
    Hey Chip–
    Great quote. I had forgotten it until now. Thanks.

  19. Thanks Dr Mike – I finally get it now! You really do a good job at explaining things in layman’s terms.
    Hi Tracy–
    I’m glad you got it. Thanks for the kind words.

  20. I hope this isn’t a stupid question, but how does fat factor into this breakdown of incoming energy? What kind of energy expenditure is involved in breaking down fat? More than, as much as, less than protein? If the body barely has to work at all to convert carbs, but has to work a lot to convert protein into glucose, what role does fat play in the process?
    The body has to work even less than it does with carbs to store fat. The real metabolic ‘boost’ comes from the protein.

  21. Indeed, we are not closed systems. The alimentary canal is a tube that allows calories to escape without being absorbed and utilized. It is the absolute amount of absorption and utilization that that determines whether one gains weight, maintains weight, or sheds pounds.
    If one could trace every calorie that enters the stomach, one would observe that some twenty to sixty percent of caloric energy passes out of the body without being absorbed into the bloodstream. Some of the energy contained in those calories is released as heat energy into the body as a result bacterial activity in the gut.
    It’s estimated that about half of fecal matter consists of dead bacteria. I personally find that if I consume more food, I have more frequent bowel movements. I simply do not gain weight.
    One would expect that variations in biochemical and physiological makeup would generate corresponding variations in absorption efficiency that would, in turn, determine whether one gained or lost weight with variations in caloric intake.
    For more discussion on this, Google “unabsorbed calories” or “calorie excretion.” Apparently, scientists who pay attention to this phenomenon are few and far between.
    I’ll Google and read, but it will take some convincing.

  22. Dr Eades,
    I am a regular reader of your blog and always find your views interesting and illuminating, however, I feel that I must point out that nutritionists DO already take account of the inefficiency of digestion of protein. The actual kcal value of protein (calculated in a bomb calorimeter) is just over 5, but it is reduced to 4 for the purposes of calculating the energy available for digestion by the body. The reason is that amino acids are metabolised only as far as urea, not all the way to oxygen oxides – which would be toxic. Urea still has chemical energy, nearly a quarter of the original chemical energy of a mixture of amino acids, hence the reduction from c5 to 4 kcals that are given in all the calorie charts.
    That being said, I agree that there still seems to be something going on with a low carbohydrate diet that doesn’t seem to be wholly related to calories – but I haven’t yet seen any research that really nails the reason!
    Hi Paul–
    Looks like I’ve got too many smart people reading this blog. I’ll have to be more careful. You are indeed correct in pointing out that the inefficiency of protein digestion has been taken into account in setting the caloric content as 4kcal/g. But I’m talking about something different. There is an inefficiency in the use of protein under all conditions (which is what you’re talking about), but there is an increase in inefficiency (that hasn’t been dealt with in setting the caloric content) when protein has to be converted to glucose because the carb content of the diet isn’t high enough to meet the body’s glucose needs. That’s the inefficiency I’m talking about.

  23. What bothers me about the “calorie is a calorie” argument is that even if we entertain that over-simplistic idea for a second, how are all these people sure that the body will compensate the decrease in calories by weight loss? Losing fat is not the only possible way.
    Our bodies could run systems less efficiently to conserve energy. What comes to mind is how some women stop menstruating on strict diets. Is it possible that their bodies somehow “decided” that instead of losing fat, it’ll shut down the reproductive system for now till food becomes available again?
    The “calorie is a calorie” idea also implies that we are a feed-forward system (calories in, calories out, net loss). This is way too simple. I like to think we are feed backward system. Hunger is a brilliant feedback mechanism and some focus should be on how to control the feedback (i.e. control hunger) instead of just focusing on the calories in.
    To avoid generalization, at least for fat is an incredible hunger suppressant.
    Hi Kay–
    You are correct. And Taubes makes the same point in his book. Hunger and metabolic state drive the calories in/calories out side of the equation. You can cut calories for short periods of time and increase exercise, but unless something changes on the left side of the equation, these efforts will be short lived.

  24. Excellent post.
    I would also say that there’s another great variable in this “food to fat” path: the digestive process. Not only in the energy necessary for the digestion itself but also the fact that since I go to the loo, there’s certainly stuff that I ate that I didn’t get absorbed.
    Also, I wouldn’t be at all surprised if the absorption of corn syrup were much more efficient than the absorption of a steak.
    Hi Mauro–
    Actually most of these digestive inefficiencies have been taken into account when the caloric content of the macronutrients were set.

  25. Dr. Eades, you point out a misunderstanding by Dr. Atkins..
    “And it helps to understand the vituperation heaped on Robert Atkins who wrote one of the most hubristic and outright ignorant statements imaginable showing a total lack of understanding of the laws of thermodynamics when he said:
    ‘When I make this claim, that you can lose more weight on a higher number of calories, I seem to be breaking the law—one of the hallowed laws of thermodynamics. Many powers-that-be get terribly provoked when I repeal their laws. But the calorie theory is a false law that is meant to be broken, and ketosis/lipolysis is the instrument for breaking it.’
    But then seem to agree with Atkins position with this statement towards the end of your blog….
    “Bear all this in mind the next time you tell someone that it is possible to lose more weight on a greater number of calories as long as those calories are low-carb calories, and that someone pooh poohs you with the old ‘That can’t be possible. It violates the laws of thermodynamics. A calorie is after all a calorie.’ Ask them precisely which laws of thermodynamics it violates and ask them to tell you how. Then sit back and watch the fun.”
    Isn’t that exactly what Atkins was saying with his low carb diet? Although I’m not familiar with Atkins writing, I would suspect that his quote may have been taken out of context (after all he did say that he “seemed” to breaking the second law). I think you need to expound on where you think Atkins’ error was.
    Hi Michael–
    Had Atkins correlated his statements with the idea that these statements were in accord with the laws of thermodynamics, and had he gone on to show how, then I think he would have been accepted instead of reviled. But when he comes out and says: I have “repealed their laws” in reference to the laws of thermodynamics no one with any scientific knowledge could think him anything but an idiot. As a consequence, this hubristic posturing probably set low-carb dieting back 50 years.

  26. Hello, nice post as ever, and so civil too 😉
    This said, I think that the main problem with the ‘metabolic advantage of LC’ term is more a thing of perspective than a chemistry thing. It would be better to speak of ‘metabolic burden of HC’ because I think it is a better characterization of the phenomenon. People who have long time a defective diet (much fat incl. transfats, very much carbs with a lot of fructose, few proteins, to few micronutritions) will starve and accumulate fat at the same time. When these people will start a LC diet, they will augment their metabolism tremendously. And the difference is probably much higher than any inherent metabolic difference between HC and LC. It is probable that a well nourished highcarber and a wele nourished lowcarber do not show a big difference. The ward studies are done on healthy young people, it would be more interesting to do one on fat diabetics.
    Hi gallier2–
    A few other commenters have made the same point. I think the overall metabolic improvement one sees on a low-carb diet is beneficial and helps them get motivated to move more and do more to continue to lose excess fat, but that’s different than what I’m talking about in terms of a metabolic advantage driven by a change in macronutrient composition.

  27. Hellistile……interesting choice of words …reminds me of Julian of Norwich and the ‘fiery tipped sword’ !

  28. Another great post Dr Mike!. You are the man! How about the thermic effect of digestion as a metabolic advantage when eating 5 to 6 meals a day vs. 3 squares? I hear that being promoted by some fitness experts. I have been IFing, but in a random fashion. sometimes once every three days sometimes every four. Most of the times I only eat 2 meals a day, maybe once a week I will eat 3 times. I really love lifting weights in a fasted state.
    Hi Carlos–
    I haven’t really seen the studies (I haven’t looked for them), but I would bet that larger meals would increase the thermic effect more than many smaller meals all of which add up to the same calories as the larger one. Why? Because the body can’t use all the nutrients in the larger meal and has to spend energy to partition them whereas more of the nutrients can be immediately used after the smaller meals. This is just a guess on my part though.

  29. I’ve also read that the proper diet (very low carb, at least adequate amounts of protein and fats) is ESPECIALLY potent when combined with proper exercise (resistance training a la ‘Slow Burn’). Is this because some of the macronutrients consumed are not actually ‘burned’ for energy, but are used as building blocks to repair and build new muscle tissue, bone, organ tissue, etc.? Or are all of the macronutrients we eat pretty much broken down for energy, then the ‘building materials’ we need reconstructed via other processes in the body, stored fat, recycled cells, etc?
    Hi Bob–
    The macronutrients we eat are used for building blocks for muscle and other tissues. But it requires energy to build muscles – they don’t just spontaneously form. So there is another loss of energy. Sometimes at the same time we’re building muscle we’re losing fat so that we don’t have an overall weight loss, but we do have a great redistribution.

  30. Hey this article is absolutely fantastic! While I haven’t had anyone mention thermodynamics specifically, I’ve heard the “a calorie is a calorie” many times. Woohoo more ammo! Thanks!
    Also, about the post from David Brown – wouldn’t that be in the category of the malabsorption syndrome thing? Or is it just a super efficient calorie burning metabolism? Maybe he can bottle his metabolism and sell it in a pill and say “Hey eat what you want you’ll just poo out the extra!” LOL. Seriously though, would that be considered a malabsorption issue or just an extra high-gear metabolism, or something else? And if that were the case, wouldn’t everyone be skinny? That’s confusing.
    Hi Lisa–
    It could be a malabsorption issue, but I doubt it. I need to read the material before I can comment intelligently. One of the other commenters is correct in pointing out that the inefficiencies of digestion are taken into account in setting the caloric content of foods. There are actually more available calories than the 4, 4 and 9 that are listed for protein, carbs and fat. The extra – non-listed – calories do more or less pass on through unused.

  31. Dr Eades i have a question about the second law. Since the law states that energy always moves from a state of reduced entropy to a state of increased entropy, Doesn’t this poke a hole in the big bang theory because if energy never gathers but always radiates how could all the energy in the universe become into a state of unimaginable reduced entropy? It’s something that i can’t get my brain around.
    Happy Friday
    Hey Travis–
    Thanks for bringing this up. It’ll give me something to work on over the weekend.

  32. Thanks Dr Eades. I had a look at Drs Feiman and Fine on this topic( Googling ‘entropy’ and ‘thermogenesis’ turnrd up this link ),
    but I have to say I found your post much more understandable than theirs.
    Hey Neil–
    Thanks for reminding me. There is this paper along with several more that I intended to link to in the post, but was in a rush to get somewhere so I posted without them. I’ll stick them up soon and add a small post to point them out to readers who don’t read the comments.

  33. Great post Mike. I see that Anthony Colpo has yet to reply. We know he reads your blog. No doubt he is scrambling through his library of Scholastic paperbacks on physiology (you know, the ones he uses for formulating HIS ideas) to combat the 2nd law of TD. We wish him luck.
    Hi Fred–
    I would imagine that since he’s such a legend in his own mind already that his laws supersede all the laws of thermodynamics. He would be better served financially spending more time trying to perfect his perpetual motion machine than in trying to peddle his poorly written, scientifically-inaccurate books online.

  34. Good post Doc. You make me smarter and that’s not always easy to do. But hey, I still have a question. My Toyota has a nice v-8 under the hood but with gas prices being what they are and all I’ve occasionally put in a little regular unleaded instead of the premium petrol that I usually feed it. Just trying to save a buck ya know, but do you think I’ve done any serious damage to my vehicle? Thanks again Doc, sure do appreciate you’re help on this.
    Hey James–
    My recommendation is that you mix a little sugar in with that gasoline. That should help bump up the available energy. Just don’t do it, though, right before you’re coming to pick me up.

  35. Hi Mike,
    Thanks for the link to the Johnson et al paper. I’ve read some of the references they use but don’t recall coming across this one. (btw, I wish I had the time and money to do detailed research on my own … but for the time being I’ll continue to let others (including you) do most of my work for me!)
    In any event the paper goes a long way to answering my question as to the magnitude of the effect, and why such small differences could be swallowed up in the error margins of other studies. The Fineman and Fein paper also supports a very small difference if all we are talking about is the inefficiency of converting a shortfall in glucose of maybe 100g or so. And as you said a few weeks back on the exercise question;
    “When an average person runs or walks a mile (it doesn’t matter which – calories are burned by moving mass across a distance) that individual burns about 100 calories more than he/she would burn sitting on the couch staring out the window.
    Now open any book of nutritional values and look up the amount of food it takes to give you 100 calories. It’s almost nothing. A half an ounce of nuts, an extra bite of pizza, a little extra half and half in your Starbucks throughout the day, a little over an ounce of trail mix, half of a granola bar, a few crackers, a half a bagel, a couple of extra forkfuls of most any casserole dish, and on and on. So, you go out and run a mile in the morning and you make up for it during the course of the day by increasing your intake by virtually unmeasurable amounts. That’s why exercise doesn’t work for weight loss.”
    Clearly any metabolic advantage of a low carb diet can be similarly easily lost – particularly so when you consider that thanks to people like Atkins many low carbers seem to have the idea that the magnitude and nature of the advantage will take care of any amount of calories as long as carbs are kept low enough (this mirrors the popular belief that small amounts of exercise justify raising intake well past what is actually expended … I think we can agree on that being at least part of the reason can’t we? 😉 )
    One thing that has always interested me is efficiency – Phinney and others find that with a period of adaptation (4 – 6 weeks from memory) physical performance on a low carb diet is restored or even enhanced. Does this mean that not only is the REE reduction advantage lost (after the calorie restricted/weight loss phase of your low carb diet concludes), but that the other inefficiencies of high protein/fat metabolism fade with time as adaptation occurs, or is this solely attributable to enzymes related to fat metabolism (not protein) … but even if it is … wouldn’t lack of adaptation interfere with the results of any study without this adjustment phase?
    Hi Malcolm–
    The metabolic advantage is small. Based on the studies I’ve looked at it’s maybe 250-300 kcal max, which can easily be undone by a few extra bites here and there.
    I think adaptation probably does make a difference in the metabolic advantage since entropy is the least during a steady-state situation. And since part of the metabolic advantage derives from entropy, this would almost mandate the the metabolic advantage decrease a little.

  36. Wow, great post. I really enjoy your blog and learn a lot from you. Thanks for keeping me up to date.
    Hi Melissa–
    Thanks for the kind words.
    I’m glad you enjoy the blog.

  37. Dr. Eades:
    You replied to Aaron Ashmann, “The GI tract is pretty good at absorbing all the food that travels along it . . .”
    I spent about 25 years gaining weight by eating pizza, tacos, fast food and a 6-pack of beer every night. I should weight about 175 lbs, and I topped out at 256. Now that I eat low-carb, I maintain my weight (180 lbs) at around 1800 – 2000 calories a day. Considering how I used to eat, I was certainly eating at least 2,500 calories a day (probably more, since the beer alone was 900 calories a day).
    If you calculate an extra 500 calories a day for 25 years, I should have weighed about 1300 lbs!
    The only explanation I can think of is that the body does NOT absorb all the calories you eat if you are overeating excessively. Oh, and now I exercise, whereas I did not for all those years.
    Any comments?
    Hi Jim–
    Your body just isn’t all that accurate. Some people don’t gain weight over an entire year. On an average diet that means that almost a million Calories are consumed and have to be balanced perfectly for no weight to be gained. It just doesn’t work that way.

  38. Dr. Eades,
    I believe you have been misrepresenting the laws of thermodynamics.
    1. Entropy is NOT a form of energy.
    2. The laws of thermodynamics apply to all kinds of systems (open and closed).
    3. Chemical reactions do not necessarily have a positive change in entropy.
    4. Total entropy increases in an isolated system, true. Which means that in an open system, entropy can actually decrease, as long as the corresponding increase in the rest of the “universe” makes the TOTAL change in entropy to be greater than or equal to zero.
    And just to add:
    The equation that (weight gain = calories in – calories out) is dimensionally inconsistent. And so is the equation that (calories in = calories out + entropy). By those two equations, one can conclude that weight gain = entropy. I can’t see how this equation can not be laughed out of any serious scientific conference.
    Someone else already pointed out the problem with your gasoline analogy, which is not trivial.
    I do enjoy reading your blog. When it’s scientifically sound and consistent, that is.
    All the best.
    Hi John–
    I agree with pretty much everything you say except for #3. I have a pretty fair knowledge of thermodynamics, but, though seemingly simple on the surface, thermodynamics, and especially entropy, are very difficult concepts to explain to laymen in understandable terms. If you would like to take a shot at it, go for it, and I’ll be happy to put up your simple explanation. I look forward to it.

  39. Heat + Food = an increased hunger greatly over what would be
    Raw + food = Normal Hunger
    This is a simple fact – and any reducing diet ignoring it is very problematic – as heating always increases the need for more useless calories – as well as destroying many digestive enzymes
    Heating Animal Protein – Dairy and Fish –
    Heating is not a problem with these – heating creates a greater hunger for calories – yes – but the body needs Fish and needs Dairy Protein(low fat un-sugared yogurt and cottage cheese) –
    The ‘average’ daily protein intake should be around 120 grams – and this is seldom met in any standard diet – American or otherwise –
    Fat – Peanut Butter and Ice cream and Sugar/Fructose
    These foods are responsible for most weight gain – usually from binges –
    An incredible amount of heat processing is used in the process of making Sugar and Corn Syrup and hence – Fructose
    It’s the Heat – although heat doesn’t add visible calories to a food – it somehow increases the hunger or need for more of them.
    If the correct Protein choices are made in the Diet – (Fish – low fat sugar free Yogurt or Cottage Cheese) – heat is not a problem with these foods – people eat too few of at best – usually
    Plant Carbs – it is a real problem here
    Fats – Coconut Flakes and Virgin Clod Pressed Olive Oil are free from heat processing – I think
    Peanut Butter – Cow’s Butter and a Host of other Fat sources are not free of heat processing –
    And this is a problem – and creates – unless these foods are carefully eaten in small amounts – for more useless calories above what is needed – whether these heat processed calories can be burned or used metabolically without body fat gain – does not mean they are without any risk

  40. Dr. Eades,
    I never claimed that I can give thermodynamics a simple explanation. I know some people who had to repeat the same thermo course three times before they could pass it (I’m a chemical engineer, and no, I wasn’t one of those people). I also agree that it is very difficult to explain it to laymen. But it shouldn’t be oversimplified, either, especially when the resulting “knowledge” that comes out of it is wrong. And saying that “entropy is energy” is just wrong.
    As for chemical reactions, what drives them is the free energy (or Gibbs’ free energy) change. The entropy change of a chemical reaction can be positive or negative. But the Gibbs’ energy change should be negative for the reaction to proceed spontaneously. A positive change in G means that energy is required for the reaction to proceed.
    The equation for this is
    delta (G) = delta (H) – T delta (S)
    or the change in free enegy is the difference of the change in enthalpy (or “heat energy”) and the temperature of the reaction times the change in entropy. We can have a negative entropy change and still have the reaction proceed spontaneously if the enthalpy change is negative enough.
    Are there chemical reactions where entropy in the reaction itself decreases? Yes.
    One example of a chemical reaction with decreasing entropy is the combination of hydrogen gas and oxygen gas to make water vapor. Another example is the creation of protein molecules from individual amino acids. Or fat molecules from individual fatty acids. Anything that produces a smaller number of molecules (in the same phase – if there’s a phase change, all bets are off) from a larger set of molecules or atoms results in less entropy for that particular system.
    But contrary to what you stated, in these reactions the “universe” provides energy to the system instead of the local reaction losing “entropy” to the universe. The energy used in macromolecule production comes from the other more spontaneous reactions occurring in the body that produce ATP, NADP, etc. So it’s true that for the entire body, as a system, there is an increase in entropy. But to state that all chemical reactions result in positive change in entropy is incorrect. (I believe that’s what you meant when you said, “Each of the many chemical reactions in the body end up dissipating energy” since you were using entropy and “dissipating energy” sort of interchangeably.)
    As you can see, I’m no good at simple explanations, but I hope you understand what I’m trying to say.
    I do think I understand the whole good calorie/bad calorie deal now, after thinking about the thermodynamics of it. The difference between ingesting 100 calories of carbohydrates and 100 calories of protein is the chemical reactions that are involved in digesting them. Some require more energy (e.g. proteins) before they become usable to the body, so not all 100 calories are available to be converted into fat. Carbs are just “cheap” fuel, energy-wise, since the digestion is much simpler and straightforward, and the resulting product (sugars) are immediately usable to the body.
    I honestly don’t see why you’d invoke the second law to explain this when the first law would do just fine, though.
    Hi John–
    I, too, passed my thermodynamics course the first time I took it when I was in engineering school. I did adiabatic expansion and steam table problems until I was blue in the face, but I did get through it with a good grade.
    You’ve still missed the point about the good calorie/bad calorie deal, though. The chemical reactions involved in digesting them are already accounted for in the caloric determinations. A gram of protein actually releases about 5 kcal when torched in a calorimeter but the caloric value to the body has been determined to be about 4 kcal per gram because about 20% is lost in the digestive process. What I’m talking about is the difference required to burn glucose directly verses having to first convert protein to glucose then burn the glucose.
    But here is your explanation of entropy for everyone to read.

  41. Hi Dr Mike,
    You wrote, “The body has to work even less than it does with carbs to store fat. ”
    You mean in the presence of high insulin, right? In low insulin state, the body doesn’t really store fat, right?
    you wrote, “The real metabolic ‘boost’ comes from the protein.”
    I just have to ask this, now that I’ve seen you actually write about it here. There is a lot of discussion on BB’s that too much protein is turned to glucose and will therefore interfere with fat-burning. In theory at least, this seems logical.
    How much protein above the minimum does it take to interfere with the mechanics/success of a LC diet?
    For example, my protein minimum is 81 g per day. How much more than that does it take to cause a problem for weight loss on a LC diet of say 30g per day, assuming a “normal” fat intake of say, 100g per day?
    Please, please! This has been bothering me for YEARS. 81g per day simply is NOT ENOUGH to control my appetite.–
    Thank you.
    Hi Elle–
    I guess I need to do a post on this subject that I can refer back to because I’m asked this question constantly…and the question is always prefaced by “there is a lot of discussion about this on various low-carb BBs… You do not convert dietary protein into sugar unless a) you’re a type I diabetic or b) you aren’t getting enough glucose and the body needs to make more. If you’re on a low-carb diet you are not getting enough carbs to meet the body’s demand so some of the protein you eat is converted to glucose. But just enough to keep your blood sugar where it is supposed to be. Extra protein doesn’t automatically convert to sugar if your blood sugar level is where it is supposed to be.
    So, the take home message is: don’t worry about protein converting to sugar. Eat as much as you want.

  42. I’ll take a stab at explaining entropy.
    Entropy is the opposite of information. The higher the entropy of a system, the less you know about it.
    Think of an egg carton containing a marble. If the egg carton is open, you can see which hole the marble is sitting in. Close it an shake it up. If you don’t open it again, the entropy is higher, because you don’t know which hole contains the marble. Similarly, the more holes, the larger the entropy, since the marble has more places to go, and you thus have less information about where it is.
    So entropy, in a sense, is an accounting of everything you don’t know, given what you do know. In the example above, we know there’s one marble and N holes. So there’s N “states” of our little model universe, and we don’t know which one is “real” (without opening the box). The more states we can’t observe, the higher the entropy. The probability that the marble will occupy any given hole is 1/N (yes, I know that’s oversimplifying a bit). Suppose you try to guess which hole contains the marble. As N gets larger, the probability that you’re right gets smaller, and hence the probability that you’re wrong gets larger. As N goes to infinity, the probability that you’ll guess the hole goes to zero.
    When you start dealing with large numbers of particles which are relevant for macroscopic systems (like people), the probabilities become overwhelmingly large (or small). With something like 100 billion billion gas molecules, you find there’s vastly more possible states where the gas molecules are spread evenly throughout their volume as opposed to showing significant variations in density. It’s not impossible for all of the air in the room to suddenly rush to one corner and stay there, just incredibly unlikely. Hence the “law” that a gas always fills the volume which contains it is really just a consequence of the 2nd law of thermodynamics: there’s so many more ways to evenly fill the containing volume than any other distribution of gas, it’s the only thing you ever see.
    This is why scientists place so much weight on the second law of thermodynamics: in the end, it’s just math, starting with very simple counting arguments. Finding a violation in the second law is like asserting 1+1=3. Even the first law (conservation of energy) doesn’t get so much respect. Why? Because the conservation of energy (like all conservation laws) is based on an assumed symmetry of the universe. In the case of energy, it’s assumed that the laws of physics do not change with time; they are the same now as they will be later. Indeed, it is thought that energy is NOT conserved for the universe as whole, because spacetime continues to expand. Since the laws of physics are (usually) written in terms of the underlying spacetime structure, changes to that structure imply violation of energy conservation.
    Entropy, on the other hand, just comes from counting possibilities. There are no underlying assumptions, other than simple mathematical ones, and in the limit of large numbers, the probability of every observing a violation of the second law becomes so small that for all practical purposes, you’ll never see it. It’s not impossible, just extremely improbable.
    Now, the body is in thermal contact with it’s surroundings. When you lose heat, to the environment, there are vastly more ways for that heat to spread throughout the environment than there are for it to return to the body (just like the air in a room). So once the heat leaves, it’s gone forever, reflecting an increase in the entropy of the universe.
    It is (obviously) possible to reduce the entropy of a particular piece of the universe. If it weren’t we wouldn’t have ice cubes, much less human beings. Ice has less entropy than liquid water, because the water molecules are no longer free to move around, so there’s less possible ways of rearranging the water molecules in an ice cube (they’re all fixed relative to each other). But the only way to lower the entropy of the water to make ice is to extract heat and release it to the surrounding environment. So the total entropy of the universe increases (by quite a lot, it turns out), even though the entropy of a local part has decreased.
    So some chemical reactions might appear to reduce entropy, but that’s invariably due to an incomplete accounting of all of the products (it’s just math). You lost something somewhere, and that something is almost always energy. Thus, to take a random jumble of amino and fatty acids in the blood (high entropy) and assemble them into the specific configuration of human muscle tissue (lower entropy) requires that some heat be lost to the universe, thus increasing entropy.
    It’s just math.
    Thanks, Dave–
    Here it is for all to read.

  43. Toward the end of her review of Taubes new book in yesterday’s New York Times Gina Kolata says the following:
    “It’s known, though, that the body is not so easily fooled. Taubes ignores what diabetes researchers say is a body of published papers documenting a complex system of metabolic controls that, in the end, assure that a calorie is a calorie is a calorie. He also ignores definitive studies done in the 1950s and ’60s by Jules Hirsch of Rockefeller University and Rudolph Leibel of Columbia, which tested whether calories from different sources have different effects. The investigators hospitalized their subjects and gave them controlled diets in which the carbohydrate content varied from zero to 85 percent, and the fat content varied inversely from 85 percent to zero. Protein was held steady at 15 percent. They asked how many calories of what kind were needed to maintain the subjects’ weight. As it turned out, the composition of the diet made no difference.”
    While this doesn’t contradict your argument, it seems to contradict the generality of the conclusion. I’m not competent to evaluatie Kolata’s evidence and would appreciate your view of it.
    Taubes mentions a zillion papers and leaves out one that isn’t even a significant paper. I’ll post more about this paper later, but let me tell you it is a nothing paper. Kolata was grasping for straws because she desperately didn’t want to give a good review to the book. She is part of the low-fat coven of food writers at the New York Times and wouldn’t want to make her sisters look bad.

  44. In practical term it is possible to apply the Laws of Thermodynamics (First and Second) only in close system where no energy coming in and no energy going out. That is the case with any mechanical engine.
    In case of human body, some energy going out, like energy excreted as metabolic waste.
    Applying law of thermodynamics on humans does explain nothing concerning weight gain/weight loss.
    I don’t agree, but here’s your comment in case others want to join in.

  45. John,
    Not to get into a pissing match but you said:

    “ shouldn’t be oversimplified, either, especially when the resulting “knowledge” that comes out of it is wrong. And saying that “entropy is energy” is just wrong.”
    Perhaps you missed this sentence in Dr. Eades’ blog:
    “(I’ve used entropy as if it is synonymous with energy when in technical terms it really isn’t, but it’s easier to think of it that way.)”
    If you look at all the comments on this thread you’ll see what this particular blog has accomplished – it has helped the layperson to get jiggy with the basic concept of ‘a calorie is not a calorie’ so that people can understand why eating 3,000 calories (when your BMR is 3000 calories) of Twinkies will make you fat as a cow and why the same amount of calories from a nice fatty grass fed rib eye steak with a garden salad laden with olive oil and avocado will allow for the skinny jeans to be dusted off from the top shelf.
    The first law of TD does NOT suffice for explaining why this is so and it IS so. And yes, yes, yes, if you eat a lot less calories you’ll lose weight too. BUT the weight lost will come from muscle mass as well as body fat stores if the makeup of the calories is insufficient in fats and protein.
    It’s not about weight loss – it’s about fat loss. It’s about altering the composition of the body and the upregulation of hormonal tone somthing that is impossible to achieve by eating like a gopher – or like Dean Ornish.

  46. I think some of the confusion about thermodynamics is because the laws are stated differently depending on whether you’re speaking of an open system, a closed system (no exchange of mass), or an isolated system (no exchange of mass or energy). You can also consider “the system” to be your body or a calorimeter or you can consider “the system” to be the Universe.
    I took PChem more than 50 years ago and misremembered some things, but I found a URL that discusses the laws for both open and closed systems:
    In an isolated system, there is no change in energy. In open system, DE = DEin – DEout where D = delta. This is what dietitians love to spout.
    However, what dietitians miss is that the Energy Out part of the equation includes inefficiency in which energy is converted to heat, which then leaves the system (your body), which is what Dr Mike was talking about.
    However, I think dietitians might understand better if one didn’t try to explain the second law of thermodynamics to them but pointed out that human metabolism is governed by enzymes, and if you can uncouple the electron transport chain so that instead of producing ATP you produce heat, you can eat all the calories you want and not gain weight.
    Some people seem to have more “uncoupling proteins” that do this, and they’re probably the ones who don’t gain weight on high-calorie diets. Uncoupling proteins may also be central to type 2 diabetes. Because beta cells require ATP as a signal to produce insulin, if you have too much UCP2 in the beta cells so they don’t produce enough ATP, then the cells don’t know they’re supposed to secrete insulin.
    There are also small molecules that uncouple this reaction. One of them, DNP, was used in the 1920s as a diet aid. It worked great. The only problem was that it killed a lot of people and for some peculiar reason lost its appeal. As one person wrote, “the treatment eliminated not only the fat but also the patients,…This discouraged physicians for awhile…”
    Hi Gtetchen–
    Thanks for the link – it looks like a good site.
    And, yep, DNP was a winner for those it didn’t kill.

  47. Thank you so much for your answer, Dr Mike.
    Please do a post on this (protein-to-glucose), if you can. This is a subject of much heated debate in the LC world of BB’s and would be beneficial to dieters “where the rubber meets the road.”
    I know that extra fat is burned up in futile cycles–thanks to you.
    So what happens to any extra protein? I need that answer for my “arsenal.”
    Thank you again for all you do for the LC “cause.”
    Hi Elle–
    The extra protein not used to build protein structures is simply burned like any other fuel.

  48. I’m waiting for someone like Kolata or Brody to put together a detailed case for low fat. Where’s the book on low fat dieting that has the depth and scientific consistency that Taubes brought to the table? If such a thing exists, I’d love to hear about it, but I’ve never been able to find anything other than the usual dogmatic parrot act (“Everybody knows that fat causes “).
    One of the keys that helps to distinguish between “real” science and BS is consistency across various threads of investigation. What impresses me about the Taubes book is how he draws together these threads, from epidemiological studies to clinical studies, all the way down to what is known about metabolism at the cellular and even molecular level. All of these lend support to the underlying hypothesis that overconsumption of carbohydrates is largely responsible for a panoply of modern health problems.
    Citation of a single study or set of studies does not refute a large body of evidence, especially when that evidence is gathered from many different fields, study types, etc. You need to attack each individual thread, show where the researchers made an error and/or why their results are consistent with a competing hypothesis. The competing hypothesis should have a similar level of evidence, again supported by multiple lines of inquiry.
    Taubes no doubt ignored a lot of research, not intentionally, but simply out of practicality. When you’re trying to understand the evidence supporting a hypothesis, you generally start with the most recent publications claiming to support the hypothesis, and then follow the trail of references back in time, hopefully coming to the “root” of the evidential tree. Lots of papers that might be considered relevant don’t get referenced in this tree, but it’s a fool’s errand to try and track down everything ever written on a topic (Taubes did a lot more than I would have expected, a very thorough job by any standard of scientific research).
    90% of published research is irrelevant (doesn’t add any evidential support) or just plain wrong (poor design, incorrect use of statistics, ignoring information). In a complex subject like nutrition or medicine, I’m sure you can find at least one paper to support/refute just about any hypothesis. Look at homeopathy: it’s a shining example of bad science. It makes no sense on any level, apart from being a placebo effect. Yet papers continue to be published in peer-reviewed journals.
    So the naysayers will always be able to come up with isolated “evidence” purporting to refute some aspect of the Taubes book (and it should be noted that Taubes really makes no claims per se, rather just saying “Most of the credible the evidence points in this direction, shouldn’t we keep looking there?”). But even if you take this refuting evidence as “true”, that still leaves all of the other evidence Taubes put forth. When somebody wants to attack the whole thing with the same level of detail as Taubes presents, I’ll listen. Until then, it’s safe to assume the squawking is little more than dogmatic hand-waving.
    I’m waiting for Jane Brody to weigh in on this whole issue. She gets a pretty righteous skewering in the Taubes book.
    Hi Dave–
    I read through all the early iterations of Gary’s book, and I can tell you that he did not ignore much research. Certainly no pertinent research. The problem is that the book had to be something that the public would buy, not a comprehensive textbook. It became a problem of what to cut and what to leave in. Gary and his editor did brilliant job of cutting yet still keeping most of the content (way more, in fact, than I thought they would be able to keep) and making the book manageable. But some studies and some paths of inquiry were of necessity eliminated. It’s one of the few books I have ever read with absolutely no fluff. Virtually every sentence is filled with meaning. I don’t think I’ve ever read a book the size of Gary’s that had as much information interestingly disseminated.
    The righteous skewering Jane got at Gary’s hands is the main reason that Kolata went after the book. She and Jane are all part of the same coven.

  49. I’ve been reading Gary Taubes book Good Calories, Bad Calories. What I find interesting about the book is that when I look back at my own childhood and teenage diet, I find that protein is the main source of calories from that diet. When I attended university and started to eat fast food (never had access to fast foods before then), I gained a lot of weight even with similar levels of exercise, although it varied. I’m gradually changing my diet to a high protein, low carb diet. I’m trying to reverse 7 years of neglect; I thought I was eating low-fat, high-carb “healthy” fast foods, but the carbs have contributed to my weight gain. I took physics in university, but I’ve never thought to apply it to my own body. Thanks for the explanation here.
    Hi Linda–
    It’s good to hear that your back on track. The nice thing about the high-protein, low-carb diet is that it can reverse 7 years worth of dietary indiscretion fairly quickly.

  50. This is my first time on this blog. Excellent post by Dr. Eades and great comments.
    I agree with Dr. Eades when he says Kolata is desperate and grasping for straws in her NY Times review of Taubes’s (most excellent) book. Kolata is literally trying to make a pig sing by stuffing a speaker in its mouth and then playing music through it.
    But Kolata really shot herself in the foot when she said: As I read Taubes’s book, I kept wondering how he would deal with an obvious question. “If low-carbohydrate diets are so wonderful, why is anyone fat? Most people who struggle with their weight have tried these (LC) diets and nearly all have regained everything they lost, as they do with other diets (including LF). What is the problem?
    The problem is that Kalata does not and can not produce a shred of data to support her statement that “most people who struggle with their weight have tried LC diets” or that those who have tried LC diets regained their weight while still on a LC diet. Kolata fatally cuts herself with the same sword she tries to use on Taubes, except that Taubes is still standing.
    Hi David–
    Welcome to the blog. I’m glad you’re enjoying it. I agree with you that Kolata is a dolt. As I mentioned in another comment, she is thick as thieves with the other members of the low-cat coven there at the NY Times, and will do anything she can to undermine the idea that anything but a low-fat diet is good for one.

  51. Dr. Mike,
    I second the request for a discussion of the paper that Kolata references. (The one where they tried to determine how many calories of different types of calories were necessary to stabilize weight.) It would seem from your discussion above that to maintain a certain weight, more fat calories would be needed than carbohydrate calories.
    I haven’t read the paper, but could you discuss why you think it is a nothing paper?
    Hi Albert–
    I will be discussing this paper and a few others like it in depth in the next week or so. Stay tuned.

  52. Hey Doc,
    Quick thought. You mentioned at some point about external temperature affecting metabolic burn. Taubes mentions the same. We spend more energy on maintaining temperature when it’s colder out.
    Taubes (and others) have suggested the obesity epidemic is mostly a gain of a few pounds across the entire spread of everyone pushing people across arbitrary lines marking normal, overweight, obese, etc.
    Gore (and others) have suggested that the earth, as a whole, is warmer than it used to be. I’m not gonna get into manmade vs. natural warming, but pretty much everyone who doesn’t work for an oil company is pretty sure it’s warmer now than in the 90’s, the 90’s were warmed than the 80’s, and so forth, back a ways.
    Is it possible that the warmer earth is the cause of the obesity epidemic rather than a story about a changing diet or the toxic environment?
    FWIW: I think it might be a factor, minor at that. I think the low fat crusade is the real changing diet/toxic environment, and, well, the beef and pork council should have fought a lot harder. Where are these guys on Protein Rich, Fat Rich diets? Why no research funding, no shell companies/think tanks to push your work? Hell, the California and Wisconsin cheese people should be on this too.
    Hi Max–
    In order to engage in the discussion as to a change in temperature playing a role in the obesity epidemic I would have to accept your premise that everyone who doesn’t work for an oil company thinks we’re in the midst of global warming. I don’t work for an oil company and I think the whole idea of global warming is bogus. Having said that, I don’t think an average temperature increase of even a few degrees is enough to make everyone fat. I’ll admit that what I just wrote is my opinion based on no research, but just my gut sense of the situation.
    If I had to blame anything it would be the increase in carhbohydrate in the diet along with the overall increase in calories (almost all carb calories) combined with a move away from saturated fats towards the inflammatory omaga-6 fats. Throw in a large increase in fructose consumption and Bingo you’ve got an obesity epidemic.

  53. Regarding Kolata’s statement quoted in the above comment:
    I for one had no real idea of low-carb before I started to read about it on the internet a few months ago. I have twice lost substancial weight on low-calorie diets and gained it right back. The whole dieting period has been one long depravation, and I couldn’t wait until I could finally get to “eat” again. With my new enlightenment om LC diets, my weight is shifting and I don’t feel the least deprived. That’s a first! And I had never heard of low-carb. (Or rather, I tried a misinformed version of it while living in the US, eating only eggs, those weird cheese slices in plastic wrapping and bologna, and couldn’t cope for more than 2 days! I thought the whole thing was a scam.)
    Regarding David Brown’s theories (maybe in some other post) I’m trying to wrap my brain around a paper by Kasper, Thiel & Ehl
    where they obviously force fed people corn oil in excess of 6000 kcal per day. I’m sure you have read it already, but I’m equally sure I will not fully understand it, and maybe it can be of interest to both you and David B
    (Please, correct my Ausländer typos before publishing)
    Hi Theresa–
    I’m familiar with the paper as is Gary Taubes. I think he even tracked down one of the authors and interviewed him, but it never made it into the book. These guys stumbled onto this and didn’t really know what to make of it. They didn’t want to confront the establishment with their findings so they published the paper, then moved on into other areas of research.
    I plan on discussing this paper along with several others along the same lines within the next week or so.

  54. A reader above, Susan posted a question which I was also going to ask- with relation to longevity and calorie restriction in particular. She wrote:
    [quote]if ancient man had a mostly meat/fat diet, how would this thermic effect be beneficial? you would think they would adapt to have a low carb diet be most efficient and energy sparing. weight loss aside, is it necessarily a good thing to crank up one’s metabolic rate. wouldn’t a lower metabolic rate be better for longevity?[/quote]
    With respect to Automobiles and the human body as an engine- don’t most engines carry a cooling system to keep them from running hot? And doesn’t some evidence show that lower body temperature and calorie restriction lead to a longer life span?
    Even though we may be more efficient machines, working harder to process protein, running hotter and faster, could me not burn out more rapidly this way?
    Very interested, thank you.
    Hi Xeta–
    Some people believe this very thing. I don’t. Why not? Because I believe we have adapted to such a diet over the millennia during which that’s all we had to eat.
    If you compare small animals to birds of the same size, you will find that the birds vastly outlive the animals despite the bird’s having higher temperatures and a higher metabolic rate. We humans have many of the same characteristics as birds in terms of expending excess calories via uncoupling the electron transport chain from oxidative phosphorylation.

  55. My head hurts from reading these comments. Can’t we just say that energy = work + heat. Isn’t that the first law, energy cannot be created or destroyed. While the second law says all the energy can’t be made into 100% work ie some heat must be made in any reaction. Hence, a high protein diet will burn more energy because more of the energy is used as heat vs other diets? PS Excellent blog

  56. Very interesting paper referenced by Theresa. The question I have for Dr. Eades is how did the researchers know the LA content of the corn oil used was as stated?
    The information I have is that commercial (highly processed) corn oil is typically used for research of this nature. The extraction of corn oil requires very high hydraulic pressures with the attendant generation of heat. Solvents are also required in the process. Presumably, neither oxygen or light were excluded during both the extraction process and in the method of storage.
    PUFAs, especially LA and ALA, are easily damaged by all the preceding factors. In view of this, it is reasonable to assume that at least some of the LA present in the corn oil was adulterated. The only way to state with reasonable accuracy the actual percentage of the various PUFAs present in any oil is to assay the material just prior to use and assay it regularly during a project of any length. I have yet to see a paper in which the researchers noted that the LA or ALA content of the oil used was assayed and confirmed as biologically active. Do the researchers simply assume that the LA content of the oil source (seeds or nuts) will be reflected in the extracted oil?
    Hi David–
    Since this was an old study I doubt that they knew the LA content. I suspect that they read it from a standardized text that the oil chemists put out.
    You make valid points.

  57. To continue on this theme, in reviewing a considerable volume of literature on diet and EFAs I have noted that you are one of the very few who has cautioned against an excess of ALA in the diet from oils such as flax and canola. This is in stark contrast to what I see as the new ‘low fat’ – ‘omega 3’. A large number of ‘experts’ endorse the proposition that we get 20 – 30 times more omega 6 (mainly from REFINED vegetable oils) than omega 3 in our diet and that for this reason we need to get all the omega 3 we can get.
    I have not yet been able to discover the source of this highly questionable assumption. But it seems apparent to me that this is an example of an information cascade similar to the one that initiated and perpetrated the low fat dogma. The extensive use of the term ‘omega 3’ and its claimed association with health benefits strongly suggests that the experts behind this campaign are not versed in lipid science. In reference to lipids, omega is a numbering convention that indicates the position of the first double bond in a PUFA molecule. Thus while ALA is an omega 3 configuration, not all omega 3 configurations are ALA. And while it is probable that the typical North American diet provides an excess of omega-6, it is virtually impossible for it to all be intact as biologically active LA omega-6. It is much more likely that, given the extraction process used for commercial vegetable oils, the use of containers that expose the oil to light and the fact that oil is typically exposed to light for weeks, if not months before being consumed, that a good portion of any omega-6 is adulterated and therefor biologically useless and even toxic. This is the real ‘omega-6 excess’ issue which is very different from an excess of the biologically active LA omega-6.
    Until such time as PUFA oils are assayed and certified to contain minimal amounts of biologically active EFAs – LA and ALA, as well as the amount of any biologically active derivitives and adulterated configurations present, the effects of PUFAs can not be scientifically assessed. It is simply mind-numbing and incomprehensible that standardized EFA oils are not, and apparently have not been, used in scientific research.
    I agree with you. And I try to avoid omega-6 oils as much as possible.

  58. What happens when you are unable to maintain a “normal” body temperature even when low carbing? How does a depressed body temperature correlate? I’ve noticed after being diagnosed with hypothyroidism that even with treatment my body temperature is lower than before (I run about 2 degrees below normal). Does this have any implications for my metabolism and while I’m not a bird how about life expectancy?
    Hi Dana–
    I don’t really know what the long-term implications of a lowered temperature are. I would imagine that if it is ‘normal’ for you to run a little cooler and if your thyroid problems are appropriately treated that it wouldn’t impact your lifespan all that much. I certainly think other factors would be more important, i.e., obesity, diabetes, high blood pressure, etc.

  59. I also make it a point to try and avoid all sources of commercially extracted PUFA oils as much as possible because there is no way of knowing the state of the various oil fractions present. MUFAs such as olive oil are probably reasonably safe.
    It seems as if we are for the most part on the same page here. Perhaps others are as well. But if this is true, there seems to be a careless disregard in the use of fatty acid terminologies was witnessed in this excerpt from the web site of Dr. McLeary.
    “A Harvard-based psychiatrist, Dr. Andrew Stohl, thought one reason responsible for the increase in depressive disorders he was seeing was related to changes in the essential fatty acid content in the modern diet. There are two essential fats required by the body. They are the groups of omega 3 and omega 6 fatty acids.(MY NOTE: Only LA-omega 6 and ALA-omega are essential, not the omega 3 and omega 6 groups as stated and LA and ALA are only essential if they are biologically active). We are consuming much more omega 6 fatty acids than required, and much less omega 3 fat. Not only is the absolute amount of each class of fats important, their ratio is also key. Today we are experiencing an absolute deficiency of the omega 3 fats and a dramatic increase in the omega 6/omega 3 ratio in our diet.”
    I vehemently disagree with the latter statement. As I previously stated, the term ‘omega’ does not in itself refer to EFAs. So the above statement is meaningless. There is no key ratio of omega 3 to omega 6 especially if the source oils are adulterated. If this is indeed the case then the optimal level for health is zero.
    At the present time here is no way of knowing what fractions, if any, of omega 6 and omega 3 in commercially pressed oils are biologically active LA omega-6 or ALA omega-3 since the majority of such oils were never intended to be a source of dietary essential fatty acids. On the other hand, fish oils are intended to be used as a dietary source of biologically active ALA omega-3 and its derivatives DHA and EPA. Therefor, the likelihood of such oils containing significant amounts of biologically active fractions is much greater. But the key as stated above is the ratio of LA omega-6 to ALA omega-3. In view of this the widespread advice to avoid all sources of omega-6 while consuming large amounts of omega-3 is probably contributing to serious health issues by creating an imbalance in the ratio of LA omega-6 to ALA omega-3 in favor of ALA omega-3.
    I’m curious. How do you define ‘biologically active’ in reference to fatty acids?

  60. The short answer is that all the existing double bonds (2 in LA omega-6, 3 in ALA omega-3) must be unsaturated. In addition, the source of the oil must be organic and unprocessed.
    EFAs and PUFAs in general have a tendency to become saturated. In particular, they have an affinity for oxygen. This is a very useful characteristic in oxidative organisms where EFAs are incorporated into the cell membrane because it facilitates oxygen transfer into the cell. Normally, nature protects EFAs by encapsulating plant oils within an airtight membrane. But any form of processing tends to disrupt this layer of protection exposing the oils to oxidation. Light is particularly destructive because it can initiate oxidative cascades.
    The commercial extraction of vegetable oils, other than olive oils which have a long tradition of use in human nutrition, and their introduction into our diet with their subsequent promotion as being beneficial to health has in my view released an ubiquitous Trojan Horse in our midst that has been flying under the radar for far too long. There are many bright people participating in your blog. You would do the world a great service by initiating a thread on essential fatty acids. This issue needs to be put under a microscope and exposed to some intense critical thinking.
    Hi David–
    I’m not sure I buy this statement: “…all the existing double bonds (2 in LA omega-6, 3 in ALA omega-3) must be unsaturated.” If the existing double bonds in LA omega-6 and ALA omega-3 weren’t unsaturated, the bonds wouldn’t be double bonds, and the LA and ALA wouldn’t be LA and ALA. The very thing that defines LA as LA is the location of the double bond; same with ALA. If they didn’t have the double bonds in the correct positions, they would be different fatty acids.
    Where have I gone wrong?

  61. True. I should have said ‘unreacted’.
    The weak nature of the double bonds present in PUFAs tends to make them unstable. The more double bonds present, the more unstable or reactive PUFAs are. Because of this PUFAs tend to readily oxidize or react to form new molecules. In the case of LA omega-6 and ALA omega-3, they can react to form toxic derivitives of the parent molecules. For the most part, these oxidized molecules and toxic derivitives are from a technical perspective still omega-3 or omega-6 configurations. In referencing the 2 essential fatty acids it is important to distinguish them from other omega 3 and 6 configurations.
    Exposure to heat, oxygen, chemicals and light, both during the extraction and storage process, can all damage PUFAs. As you point out in The Protein Power Life Plan, in 1910 most of the vegetable fat in our diet came from actual vegetables. Now we get 3 times as much vegetable oil. But we do not get the majority of this oil from vegetables or what I call ‘native sources’ in which these oils were protected from damage until consumed. The majority of vegetable oils we get in today’s typical diet are from refined vegetable oils stored in clear containers which expose them to light initiated oxidation. This process destroys the essential qualities of LA and ALA 1000 times faster than oxygen alone. Dark glass containers reduce, but do not eliminate, this effect. Oils must be stored in opaque containers (preferably glass) and refrigerated.
    Finding oils that are a source of LA omega-6 and LA omega-3 that meet the criteria essential for intact, biologically active oils is difficult. In view of this, assuming that commercial vegetable oils are a good and especially a safe source of EFAs is unwarranted. The only prudent course is to assume that all sources of commercially refined or improperly stored oils (even those properly extracted), whether hydrogenated or not, should be considered suspect and avoided. This includes the highly touted fish oils most of which are not sold in opaque containers.
    Hi David–
    This I agree with completely.

  62. Now I understand how ‘thermodynamics’ is used to perpetuate the ‘calorie is a calorie’ myth.
    It is obvious that a calorie of gasoline (carbs) has the same energy content as a calorie of coal (protien). But we would need to start with a lot more calories of coal (protien) if we had to convert coal (protein) to gasoline (carbs) first before we use it in your gasoline (carb) powered car… unless we believe in magic/ myth of 100% conversion efficiency.
    Thanks once again for the terrific job as usual explaining it to us.
    Perhaps you can help me with this … I have read Protein power, but have the following questions:
    1) If I am eating zero carb and lots of protein, some of the protein gets converted by the liver to generate the minimum essential glucose and protein goes to repair/ build muscles/ tissues. What happens to the excess protein? Excreted by the kidneys? What is meant by “burnt for fuel”?
    2) In above scenario, how is fat used for energy? I have read your blog on fat used by the liver for the protein conversion to glucose that releases ketones which the body uses as fuel. Is this the main mode? Are there other ways that fat is burned?
    3) What happens to excess dietary fat such a in a low insulin environment? Excreted? stored?
    Thanks once again for the daily education.
    Hi guru–
    The excess protein is broken down and oxidized just like any other fuel.
    Fat – both dietary and from the fat cells – gets burned in the mitochondria. Some of the fat is partially broken down into ketones, which the body uses to replace some of the glucose. I wrote a long post on this subject here. It should answer all your questions.

  63. Well….I’ve read all your post and all the responses…not because I’m really into this kind of thing but because my 9 year old grandson is overweight and we were discussing the best way to help him fight the problem. He is very energetic and gets quite a bit of exercise…lots more than his 11 year old brother…but he continues to gain weight.
    We are cutting out almost all sweets and drastically reducing the carbs in his diet so I think based on what I’m reading that we’re on the right track.
    The big question that had me searching the net was created because of a difference in opinion as to what an “efficient metabolism” is. One of us says the 8 year old has a more efficient metabolism because he uses more energy but still has excess fat. One says that the 11 year old has a more efficient metabolism because his body burns his calories even though he is less active….
    I hate to admit that even after reading all of the above posts I still can’t figure it out…
    Can anyone help?
    Two people who are the same size consume the same number of calories. One of these people loses weight, the other doesn’t. The one who doesn’t lose would have the more efficient metabolism, at least as I understand it. That person’s metabolism would more efficiently store calories instead of wasting them. Efficient metabolism isn’t really a scientific term that has a specific definition. But if it did, I suspect it would be the one I just gave.

  64. Hi,I’m trying to understand all of this and have a question.Atkins said that we should not stay in ketosis for more then a year…is this wrong with all we know now??? Gary Taubes says he eats virtually no carbs so he would be in a permanent state of ketosis would he not? I love it,hunger is controlled,feel so much better but am confused now if I should ‘up’ the carbs slowly as the plan says or enjoy what I’m doing for good.Please help!!!!!
    Paleolithic man ate a very-low-carb diet most of his life. People who stay on low-carb diets tend to adapt and usually don’t stay in as heavy a level of ketosis as those just starting a low-carb diet. Besides, ketones are normal fuels for the body, and many tissues prefer them to anything else.

  65. I only just now discovered this article.
    Thank you. It explains beautifully the advantage of Protein-Power.
    I do love that 2nd law of thermodynamics !
    Glad you enjoyed it.

  66. Warmest greetings to everybody from Belgrade, Serbia.
    Maybe you’ll be glad to hear these posts are praised internationally.
    It seems like all the words of admiration to Dr. Eades and his work have been spent out, so (although I have a great desire to) I won’t bother to say anything impressive or extraordinary, I shall simply agree and confirm what have already been said.
    Being on LC diet 7 days for the first time in my life, and having read extensive ammount of articles on this subject, stil some questions remain unclear, and I found them somehow very important from the practical point of view:
    1. I want to lose fat, not only weight. It comes logically to me that I have to intake less calories in the form of protein+fat (which are approx. fifty-fifty in my diet)in order to start burning body fat. Am I right? It makes no sense to me that I can eat fat+protein w/o control and still lose fat, even LC dieting.
    In other words I have hard time to calculate the wise number of fat+protein calories which will lead to the most efficient fat burning regime.
    If it takes long time and space to explain, maybe you just refer to a link.
    2. Is prolonged ketosis per se related to health risk, irrespectively of KB concentration in the blood. I mean, is it legitimate to say there is increased blood concentration of KB, if we assume that all the excess of KB is being excreted through urine? Or more precisely, is this transient state of raised KB levels in the blood before being eliminated harmful? Then maybe it will be better to burn all the excess with exercise rather than waiting to be eliminated. OK, I know, some exercising is always welcomed. Then, is it better to take long walks for hours, or to do 30 min aerobic exercise on daily basis?
    Again, besides your direct answer, I’ll appreciate if you link me to useful articles on this issue.
    3. The last, but not the least, what is your professional opinion about Metabolic typing? This approach is completely new to me, just to find out that Internet is full of respective questionnaires. Of course, I couldn’t resist them, and what comes out as a result is that I belong to Protein type with recommended 50% fat:30% protein:20% carbs diet proportion for the rest of my life in order to stay slim and healthy.
    Is there any reasonable scientific support for such a typing?
    Well, I realized the post is dedicated to thermodynamics and weight loss and I happen to be off-topic with my questions. I apologize. I simply was not enough eager to read all the previous posts. Guru had similar questions, but when I tried given link for further explanations it didn’t work (and still doesn’t work, maybe you can check out what is going on).
    Oh, I would almost miss to mention that I’m in a serious “negotiations” with my husband to start with the intermittent fasting.
    Dr. Eades, I feel extremely lucky to come across to your Protein power web site.
    P.S. English is not my native language. Sorry for the spelling, grammar and style mistakes.
    Hi Ljubica–
    Welcome to the blog. I’m glad you’re enjoying it.
    In answer to your questions…
    1. Yes, you need to watch your calories. I’ve received so many questions about this that I’m going to do a post on it soon.
    2. No, prolonged ketosis in not a health risk. Only if an individual is a type I diabetic is ketosis a risk. All others have built-in mechanisms to shut of ketone production before they become a problem.
    3. I think Metabolic Typing is bogus.
    I’ve fixed the link in Guru’s comment so that it goes to the appropriate post. Here is the link.
    Keep me posted on the negotiations with your husband about the IF.

  67. Dr. E,
    I’ve heard that cold water burns calories because our bodies have to heat up the water in order for it to be used. But at the same time, I’ve heard that we use some of energy keeping our temperature low enough, so wouldn’t that mean the cold water would help this process and thus not burn more calories? What do you think?
    I should probably stick to mountain biking for keeping the fat low I guess 🙂

  68. Your range of knowledge is remarkable. As is your ability to explain things. Just a quick note that I appreciate your blog tremendously, and will continue to read it going back to your first post as I find time.
    FYI, not on your blog roll, another blog I’ve read through and found to be quite informative (and compatible in most ways with your ideas, I think):
    And while here, here’s something I wrote in a private forum earlier today, FYI:
    An Austrian study ( ) indicates that higher levels of D3 correlated with longer lifespans. Period. In other words, higher levels of D3 reduce the all-cause mortality rate. There’s simply no man-made drug that can claim anything close to this.
    The study included 3,258 with an average age of 62 year, and over an average follow up of about 7.5 years just over one-fifth had died. The study concluded that people with the lowest blood levels of D were 2.5 times more likely to die from cardiovascular disease, and twice as likely to die from all remaining causes, such as cancer. Lower D levels are also associated with higher CRP and other markers of inflammation.
    A second recent study (13,331 people enrolled) comes to the same conclusion, this time by the Albert Einstein College of Medicine. Can’t find a link. The lead doctor was Michal L. Melamed, M.D. if anyone wants to try to find it.
    Note that various studies have reported that most Americans are deficient in vit. D, up to 95% of those in northern regions of the States. And this is one of the cheapest supplements available. There’s no reason anyone should be deficient.
    Here is the link for the Melamed study:
    Neither the Melamed nor the Austrian study you linked to proves that Vit D reduces all-cause mortality. Both these studies show there is a correlation between low Vit D levels and increased all-cause mortality, but that’s not the same as proving that vit D levels have anything to do with mortality levels. Correlation is not causality.
    In order to ‘prove’ that Vit D reduces all-cause mortality requires a randomized, placebo-controlled trial, which, as far as I know, hasn’t been done in humans.
    I believe that Vit D is extremely important for good health and that it probably does decrease all-cause mortality, but neither of these studies proves it.

  69. Hi Doc,
    Love your blog (obviously, as I’m in the archives). Sorry for the late comment, but I had a question that I didn’t see asked in any of the comments: doesn’t the fact that the low-carb diet consisted of 24% protein and the low-fat diet consisted of 12% protein cast doubt on the idea that it was the non-protein composition responsible for the increase in metabolic output?
    Unless I’m misunderstanding your question, I think that was the point of the article in AJCN. According to the authors, it was the increase in protein that brought about the increased metabolic output.

  70. It just seemed from your comment immediately after the study excerpt — “Bear all this in mind the next time you tell someone that it is possible to lose more weight on a greater number of calories as long as those calories are low-carb calories, and that someone pooh poohs you with the old ‘That can’t be possible. It violates the laws of thermodynamics.” — that you attribute the increased calorie burn to the difference between carb intake, when it seems like it might very well be the difference in protein intake. Sorry if I misunderstood. I’d be interested to see a similar study that kept protein levels the same and just varied the carb/fat components.
    I see what you mean now. I guess by saying low-carb calories that I was implying higher-protein calories since most low-carb diets are higher in protein.

  71. Let me preface this comment by explaining that I am a fan of low carbohydrate diets, and that I am looking forward to picking up a copy of Dr. Eades book. However, his thermodynamic explanation is very flawed. I hope he reads this post and considers modifying his post.
    A calorie is a unit of energy. Other units of energy include British Thermal Units (Btu), watt-hours, Joules, horsepower-hour, and so on (energy reflects power delivered over a period of time. Thus, “watts” represent power, while watt-hours represent energy expended.)
    Entropy is not energy. Rather, it is a description (and I am speaking loosely here) that characterizes the “quality” of energy. Without diving into the thermodynamic depths, processes that occur spontaneously always result in a net decrease in overall system quality (somewhat confusingly, this quality is defined in the negative as Entropy. Thus, a spontaneous process results in a net increase in entropy.)
    Dr. Eades correctly identifies the first law of Thermodynamics, which states that energy is conserved (though in fact, the law actually codifies the conservation of mass-energy. However, since we are talking about chemical rather than nuclear reactions, his version is more than good enough.) The Dr. errs, however, in suggesting that the second law somehow gets around the first law. It most certainly does not. And as I mentioned above, the units of energy and entropy (which is Btu per poundmass-degree F) are incompatible. Thus, his equation “calories in = calories out + entropy is flatly wrong. If we may use an analogy, consider salt water. The volume of water can stand in for energy, and the salinity (saltiness) can stand in for entropy. The equation proffered here would be akin to saying:
    5 gallons in = 4 gallons out + 35ppm salt
    It doesn’t fly, nor can one craft a logical linkage between gallons and saltiness.
    Where the error? I think I know. Remember, energy must always be preserved under the first law.
    Food represents stored energy. Whatever energy enters our bodies must be accounted for by an energy balance. Here is the correct equation:
    Calories in = calories out to generate heat + calories out to perform work + calories stored (as fat) + calories discarded (excreted as waste.)
    Note that entropy cannot be a part of this equation because the units don’t match. Does entropy increase for this reaction? It most certainly does. But that has NO BEARING on the primacy of the first law. All energy must be accounted for.
    Why, then, do low carb diets seem to allow weight loss with equal or greater caloric consumption than traditional diets? Well, the only component of our energy balance that is unexamined is the last term. There seems little doubt that our waste products must have a much higher content of unused energy than they would under a traditional diet. In other words, we are simply passing through a portion of our food energy “unused”. And a simple series of calorimeter tests should be able to prove this. Though I also think that low carb diets remove an awful lot of junk calories that we don’t even notice we consume (i.e. the “calories in” term probably goes down for many low-carb devotees.)
    Thus, the “calorie is a calorie” nugget is not (and cannot be) rejected. It holds, and will always hold. However, in the face of successful weight reduction, a fully elaborated energy balance will – must – lead to a conclusive source of where the energy is going.
    I am not writing this to be a smart-aleck. As a believer in this type of diet, I think it is very important not to present confused or erroneous description about what is and is not known about them. Rejecting “a calorie is a calorie” as being somehow subverted by some diet will never convince a skeptic schooled in engineering or physics because 200 years of thermodynamic studies have verified it to be true.
    I think, though. that determining the source of the diet’s success should not be difficult. We either unknowingly reduce our total caloric input with a low carb diet, we excrete more energy dense waste produces with a low carb diet, or a combination of the two. If our metabolism and level of activity remains generally consistent, these are the only option.

  72. Jim Turner,
    You are pretty much on the right track. What you have overlooked, however, is gut microbes. About 2 kilograms of gut microbes inhabit the digestive tract. As they multiply, they generate heat. This heat diffuses into the body and probably should be considered part of the body’s temperature regulating mechanism.
    The amount of microbial activity is determined by the amount and quality of food intake. A diet rich in all of the nutrients required for efficient gut microbe multiplication will produce more dead gut microbes in the feces than a diet containing large amounts of empty calories. In addition, increased microbial multiplication means more heat energy generated in the digestive tract and less energy absorbed into the bloodstream.
    Since each gram of microbes (dry weight) represents 5 kcal of heat energy that did not get absorbed into the bloodstream in caloric form, one can calculate the amount of heat energy generated daily by gut microbes. If a person produces about 1 ounce of stool per 12 pounds of body weight, a 156 pound individual would generate13 ounces or 369 grams of feces. Let’s say the dry weight of the feces is 25% of that or 92 grams. Since 50 to 60 percent of feces is dead gut microbes, the maximum dry weight of microbes would be 55 grams. Multiplied by 5 kcal per gram yields 275 kcal of heat energy.

  73. It’s the hormones Jim, not the calories. A calories is always a calorie yes, but this is beside the point. The composition of the calories matter and they matter a lot.
    The more fat you store the hungrier you’ll become. The more carbs you eat, especially the refined kind, the more fat you’ll probably store.
    As Gary Taubes points out in his book, it’s all determined by the hormonal regulation of the fat tissue and the effect of the nutrients consumed on those hormones.

  74. That says nothing about the quality of the protein and carbs you take in. The gasoline analogy is slightly off, because your comparing apples (carbs) to oranges (protein). In other words, all proteins are not created equal, just as all carbs are not created equal. To be more accurate, in reference to your gasoline analogy, higher quality protein will result in less entropy than lower quality protein, and more entropy = good. I’m not so sure the goal of diet should be to force your body into it’s most inefficient state. What about the nutrient quality of the food you consume? What about the taxing effects on your digestive system and other systems in your body? There’s too many other variables in play to simply christen this as the ultimate weight loss plan.

  75. Doctor,
    I’m a big fan of Gary Taubes and think he represents the Enlightenment after the Dark Ages.
    I agree completely with you regarding the biases of Kolata and Brody, but your using the term “coven” several times to describe them betrays a dated, sexist mindset. You’ve conjured up a gaggle of old women/witches chanting spells with malevolent glee as they stir the putrid cauldron of their outdated ideas. I guarantee you would never define a group of men who hold ideas you disagree with, as a coven.

    1. You wrote:

      You’ve conjured up a gaggle of old women/witches chanting spells with malevolent glee as they stir the putrid cauldron of their outdated ideas.

      To my unenlightened mind, you’ve hit on the perfect description of Kolata, Brody, Burros et al. Do you have a better word to describe them?

  76. I did enjoy your article, but I need to point out that your gasoline analogy is wrong. The difference in gasoline grades comes down to the percentage of octane molecules vs. heptane molecules. 91 octane gas contains 91% octane molecules. Their isn’t anything actually over 100, but some racing fuels are labled as such to indicate proprietary blends more resistant to detonantion. The fact is that the higher the octane percentage, the more resistant the fuel is to detonation. Premium fuel actually burns less efficiently, but this is precicely why its required for high performance engines running more advanced timings and higher compression ratios. Where a lower octane fuel would detonate before spark (a big problem) the higher octane fuel will resist this. More than you ever wanted to know about gas i’m sure, but had to explain. Otherwise, great article.

  77. God bless you for addressing the most misquoted issue by the most misguided of fools across the internet.
    They cling to the first law like bible but do not even understand it, nor can they explain it in simple terms. They fail to see that calories stored = calories in – calories spent could actually look more like calories stored = calories in – calories spent – “any number of other uses the body may have for that food resource besides energy”
    In their small minded and narrow view, the assume that every ounce of every meal is used solely for energy. They ignore that fact that sometimes useable energy is literally excreted away such as ketones in the urine, or even sugar in the urine. Obviously, if energy left the body, the only way possible is to burn it up with exercise, or it gets stored right? I am no physics expert, but to state that we do not sometimes pass useable fuel in our excrement flies in the face of facts as well.
    I know enough to know I know next to nothing. I have noticed that the truly competent people are the ones that are open to learning and admitting they may not have all the answers. I never find those people supporting the current “Heart healthy balanced approach to nutrition”. The more we learn, the more we should be realizing we need to learn and that we know very little. Constant certainty is the mindset of a fool, and clinging to dogma the mindset of a blind fanatic.
    Thanks for expanding my knowledge. Sadly, I will not get a chance to use it to convince believers that a calorie is a calorie is incorrect. They would rather listen to Jillien Micheals than Einstein in physics circles.

  78. I’ve invoked the thermodynamics argument against my mom concerning weight gain/loss before. I said that if people exercise, they won’t have weight problems, though they may gain muscle, but if they don’t exercise, then of course they may start having weight problems (more energy being used up as opposed to not, when sedentary). She’s of the school of thought that there are people that cannot do anything about their weight regardless of anything (Nutty Professor movie logic), and I know better due to my own experiences with working out and being sedentary. This is a good article; good enough that I had to comment on it years later. I would have loved to have it handy when I argued weight problems with my mother however.

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