I recently received a letter from a reader that asked about the protein-sparing effect of carbs. He sent me the address of a bodybuilding website he had been reading and wanted to know if what the guy who wrote the material said was true.
The basic premise of the piece is that in order to keep from losing muscle during dieting, one has to eat carbs. If no carbs are eaten, then muscle vanishes, or so he would have us believe. Is this true, the reader wanted to know. Let’s take a look.
Here are the pertinent paragraphs from the website:

The first thing you may think of is protein. Protein builds muscle. You learned that in the high school weight room. Protein in excess, however, can be used as energy or converted to body fat. Using protein as energy means less body fat is being used as energy. So, having the right amount of protein plus a little extra “just to be sure” you have enough is optimal, but gross overages of protein isn’t going to help you build muscle or retain it.

Believe it or not, carbs are key to retaining muscle. Carbohydrates and insulin have been targeted as the deadly duo in obesity and weight loss for very good reasons. However, even though excess carbs will make you gain fat fast, the silver lining is that you gain and retain muscle through the same mechanism.

Even when dieting with a lower than normal carb intake, your carbs can be targeted to help you retain muscle, maintain energy levels, and keep your metabolic rate high.

The anabolic effects of carbohydrates have been well documented since a 1940’s study showed them to be “protein sparing.” Compared to a fasting group, those with carbs (still no protein) lost only half as much muscle as those without carbs. Throw protein in and you get the same effect just at a higher level. Those with less carbs lose more muscle. Protein is certainly still king in the body’s anti-catabolism campaign, but carbohydrates are just as important.

Reading these paragraphs gives meaning to the old saying: “A little learning is a dangerous thing.”
Let’s look at what we know for sure about biochemistry and see where our bodybuilder went wrong.
What do we need to maintain life? We need a source of energy to keep our bodily functions humming along. We need blood sugar to feed our central nervous systems, red blood cells, and a few other tissues. And we need water.
Let’s assume we’ve got plenty of water, but we have no food to eat. How do we survive? Where do we get our energy and our blood sugar if we don’t eat?
We get our energy from the breakdown and release of stored fat. The fat we store away as adipose tissue is our energy reservoir, and that’s where we go when we need energy for all our cellular processes. Most of us, even those of us who are not overweight, have plenty of stored fat to last us a long time. Somewhere in one of our books I made the calculation that the amount of fat stored on the body of a 150 pound man was enough to allow him to walk from St. Louis to Miami (at least, I think those were the cities) without eating.
During starvation we get our blood sugar primarily from our muscles. Just as adipose tissue is the reservoir for energy, muscle is the reservoir for blood sugar. We get some sugar from the breakdown of fat, but not much. Triglycerides, i.e., stored fat, are made of three fatty acids attached to a glycerol backbone. When the fatty acids that we are burning for energy are stripped away from the glycerol, the liver converts these left-over glycerol molecules into glucose. Most of our sugar, however, comes from the breakdown of muscle tissue. The liver converts certain amino acids that make up muscle into sugar in a process called gluconeogenesis.
If we starve, our fat stores gradually ‘melt’ away as we use the stored fat for energy and our muscle mass diminishes as we breakdown muscle tissue to provide sugar.
Let’s say that during our period of starvation we find a bag of sugar. If we eat that sugar in amounts small enough to provide sugar to all the cells that need it, we won’t have to break down muscle tissue. We’ll be getting our energy from the fat we’re breaking down and we’ll get our sugar from the sugar, so we’ll retain, or spare, our muscle tissue. From this fact of biochemistry has arisen the notion that carbohydrates are muscle or protein sparing, which they indeed are under starvation conditions.
But what about when we eat? What happens under non-starvation conditions? Let’s say we’re dieting to lose weight. We create a caloric deficit and we burn our stored body fat for energy. If we’re on a low-calorie, high-carbohydrate diet we use the carbohydrate to provide the blood sugar we need, but at the expense of driving up insulin levels and stimulating the fat-storage process. If we’re on a low-carbohydrate diet, however, where do we get the sugar we need to maintain our muscle mass? From the protein we eat.
It’s important to eat plenty of protein while on a low-carbohydrate diet so that the dietary protein can be converted into blood sugar as needed. The author of the bodybuilding piece cautions against consuming too much protein because he believes any excess protein will be converted to fat, which is really stretching the biochemistry. Nature has designed our biochemistry to be efficient. The conversion of protein to fat, although possible, is extremely inefficient, and any excess energy from the excess protein would likely be more than used up in the conversion. As a consequence, dietary protein turning to fat is not something we really need to worry about. Dietary protein will convert to sugar, however, so that dietary protein, like dietary carbohydrate, is protein sparing.
The best way to lose excess stored fat and maintain (or even build) muscle is to eat plenty of protein to provide the building blocks for new muscle and to convert to blood sugar as needed while keeping overall calories low enough so that fat is burned to make up the energy deficit. The best diet to follow in order to accomplish all this easily is a whole-food low-carb diet. Protein is high, calories are low, and the limited carbohydrate insures that insulin levels remain low so that the fat easily flows from the fat cells and makes its way to the cellular furnaces for burning. (Click here for an earlier post disussing the low-calorie nature of low-carb diets.)


  1. As long as we are talking about bodybuilding “wisdom,” where does the idea that you should take about 30 grams of protein every three hours come from? What, if anything, is true about it?
    Hi Imsovain–
    I have no idea where that idea came from. If one consumes 30 grams of protein every waking three hours, it adds up to about 150-160 grams per day, which is a reasonable amount. Maybe the idea arises from the notion that protein can’t be stored (what about muscle?) so it needs to be taken in measured amounts. Wherever it came from, it needs to go back, because it makes no sense.

  2. Dr. Mike, that’s the kind of post I love. You’ve explained a complicated subject so simply and clearly that an ignoramus (such as myself) can not only comprehend it, but can also explain it to other ignoramuses and thus appear to be something other than an ignoramus. (Well, maybe I should stop at the comprehension part lest I become one of those “teachers” with dangerous knowledge like the subject of the post.) I’d love to repay you for your teachings someday, so if there’s anything you want to know about building a wall from adobe bricks give me a call and I’ll explain the whole process to you. And I’m sure that even at the half-ripe old age of 59 you’ll still have plenty of muscle to put your wall-building knowledge to good use.
    Is this an example of a Man Crush that I’ve been reading so much about lately?

  3. Only wanted to point out, that the central nerve system can, in fact, use some energy from the fat. It was shown during starvation, that the need for glucose (and thus conversion from protein) to decrease with time. It can only be explained if the brain gets its energy from something else as glucose, and it seems that ketone bodies can be this source. We shall not forget that baby exclusively fed mothermilk use mainly ketones as energy source for their brain.
    Hi Patrick–
    I intentionally left any discussion about ketones out of the post for purposes of clarity. During a fast the central nervous system begins using ketones to reduce the amount of glucose it normally uses, reducing the rate of muscle breakdown.

  4. When I talk with other PCOS women about Protein Power and how much it tends to help, I get a lot of “I am afraid to eat so much protein–with all this free testosterone, won’t it make me musclebound? I don’t want to look like a body builder!” (And similar nonsense) You would be amazed at the preconceived notions people have about protein…or after all these years, maybe you wouldn’t.
    Hi Anne–
    You’re right, I’m not surprised.
    The sad part of this situation is that if these folks followed Protein Power they wouldn’t have the free testosterone in fairly short order. One of the problems with insulin resistance is that elevated levels of insulin convert estrogen into testosterone in women. Were they to lower their insulin levels, which is easily done with a low-carb diet, they wouldn’t have nearly as much free testosterone to worry about. But, that aside, their free testosterone won’t convert the protein into muscle as they think it will. And, even if it did, were I a woman with PCOS, I would much rather look a little buff and cut than carry too much body fat.

  5. Totally cool and that makes sense. I knew about protein converting to blood sugar, but not about the body using muscle to keep blood sugar up when starving.
    I do try to keep my protein high, though I’ve tried to lower it a bit since reading the story of a woman who was stalled until she cut back the protein a bit. What is the optimal level of protein? I can sometimes eat as much as 1g per pound of body weight, which I know is safe, but is it too high for weight loss?
    I was losing muscle very fast when I first started losing weight. Adding a protein shake post-workout helped me lose more fat and less muscle.
    My trainer recently said I was losing muscle and gaining fat (this is up for debate, but could be true), so I now take my protein shake out on the gym floor with me (rather than waiting until after the workout is finished), do my weights, then drink the shake while doing my cardio. That way I get 20g of protein as soon as I finish with the weights.
    Hi Victoria–
    The optimal protein issue is a tricky one. It is different for people on a low-carb diet as compared to those on a high-carb diet because of the protein-sparing effect of carbs.
    The central nervous system, red blood cells, and other tissues requiring glucose for energy use about 200 grams per day. If one takes in, say, 30 grams of carb per day on a low-carb diet, then the 170 gram deficit has to be made up from the glycerol in stored and dietary fat, dietary protein, and/or muscle protein. If you figure that 30 or so grams can come from the glycerol, that leaves 140 grams that must be made up from protein either from dietary sources or from muscle. And, since not all amino acids convert to glucose there is not a 1 to 1 conversion from protein: more protein is required than 140 grams. If the person in question has been on a low-carb diet for a few days, that person is likely to be making ketone bodies, which the brain can use in place of glucose to a certain extent, lowering the overall glucose requirement to somewhere between 130-150 grams per day. Given this, then the 30 grams of dietary carb and the 30 grams of glycerol from fat can make up 60 grams of the, say, 140, required, leaving 80 grams to be met by protein. Is it all clear as mud?
    The point is that more protein is required on a low-carb diet because a substantial portion of it is used in making glucose. For my patients on maintenance I recommend at least 0.7 grams of protein per pound of body weight. More if they’re particularly active.

  6. Yikes, you’re right. After re-reading my comment it does sound like a man crush. (Too bad I didn’t forget to type in lowcarb on that one.) I used the word love a couple times and then there’s that reference to your muscles-a-plenty. Next time I’ll be more careful and set my flattery filter at a normal level of toadiness so my rainbow side isn’t so much in touch that it overpowers my hombre side. Maybe some of that free testosterone would help me.
    Don’t get me wrong; I have nothing against man crushes as long as I’m the object and not the perpetrator. And you, of all people, know how much I appreciate a good toady when the chips are down.

  7. I think that what bodybuilder sites tend to ignore or dismiss is that insulin is not the only anabolic hormone involved in muscle mass development. I think they forget or don’t know that it is in fact Insulin-like growth factor-1 (IGF-1) that has a more prolonged effect in muscle protein synthesis. Even more important is the fact that in order for IGF-1 to be released, there needs to be a little bit of growth hormone release as well to trigger the release of IGF-1, which can act during the next 20+ hours after a very intense workout such as that of a bodybuilder. Loads of sugar, however, are one of the best ways of missing the growth hormone boat as its release is hampered. You also wrote about that in your books.
    I’ve had similar questions in the past regarding the amount of protein we eat on Protein Power and the ‘risks’ of uncontrolled production of sugar through gluconeogenesis. What seems to be missed by some popular naysayers is that just because there is a certain amount of protein coming in the diet, that doesn’t mean that glucose is going to be made immediately without any hormonal regulation. Uncontrolled diabetics may be a special case because there may be overproduction of glucose, precisely because they’re unresponsive to insulin so gluconeogenesis can’t be shut down efficiently.
    As a side note, when I was reading comments about stalling while eating more protein, something that has also been discussed in the past on the Protein Power discussion board, is that since protein also helps keeping lean body mass from vanishing, weight loss tracked via the scale starts to lose its meaning. Body recomposition (i.e. change in clothes sizes and/or body fat percentage measurements) instead of ‘total’ body weight, on the other hand, is a better way of tracking any changes. This is even more pronounced when people incorporate regular resistance exercise along with Protein Power.
    The argument all the time is that is all we say seems to be true, then why is it that bodybuilders aren’t obese? The question would be relevant if we didn’t consider that bodybuilders are in one end of a spectrum of exercise… Even their diets are tailored to their ‘specific’ requirements. The problem seems to be that some people like to apply the principles of the bodybuilder’s diet to non-bodybuilders or even ‘sedentary’. It is no wonder what would happen to a bodybuilder who keeps eating the same way without exercising any more… where would all those carbs go? Exactly where you think they do.
    Hi Gabe–
    I think you’re right on the mark. It is the IGF-1 that’s important, which does require a little spurt of growth hormone. The growth hormone can be completely blocked by dietary carb immediately after the workout, even if consumed in only tiny amounts.
    The recomposition issue is an important one that many people lose sight of in their focus on weight loss. No one sees weight; everyone sees size. It makes much more since to work on reducing size, but it seems that everyone monitors themselves on the scale.
    Thanks for writing.

  8. Sir Hola..given that your work has a paleothrust/bent in premise would you be prepared to comment on fasting and its uses to the ‘uman system, pleasum, given that we of course evolved to have periodic fasting given the erraticism of the enviornment in which we lived within.
    Hunger was of course the natural state of man til uber recently and though most all the worlds religions use fasting as a way of clearing consciousness/shifting biopsych blockages its seems its seldom ever mentioned unless by people who are wearing purple or dancing around with stalactite swinging from their swedes(heads) i.e people who don’t come off as being partic. well informed i.e in this case YEE !
    Would you or your MRS be prepared to open up about fasting and its problems and efficacy’s ?
    Thanks muchly.
    Simon (Fellows)
    Hi Simon.
    Good to hear from you; you’ve been lying low lately.
    I’ve given a lot of thought to the fasting issue. I try to look at everything through the lens of our Paleolithic background, and based on that I can only conclude that fasting–at least in the short term–had to have been a common occurrence for our early ancestors. The medical literature is rife with papers showing multiple health improvements with short term (i.e., a day or so) fasting. One of the more recent papers demonstrated the same thing that Zammet found 15 years ago, namely that pulsatile insulin secretion (that found when episodes of eating are separated in time, i.e., no constant snacking) increases insulin sensitivity in the liver whereas constant insulin stimulation (like that found in people who are always on the eat) promotes liver insulin resistance.
    On the whole the data seems to show that going a day or so at a time every now without food is a pretty good thing. Even limiting food intake to a couple of times a day without between meal snacking seems to be a good thing. I don’t know where this nimrod advocating the latest eat-every-three-hour diet got his data; it sure wasn’t from the medical literature. I guess if you tell people what they want to hear…
    Thanks for writing.

  9. >The recomposition issue is an important one that many people lose sight of in their focus on weight loss. No one sees weight; everyone sees size. It makes much more since to work on reducing size, but it seems that everyone monitors themselves on the scale.<
    I’ve never been able to gain muscle, no matter how hard I hit the weights or how much protein I eat before and after my workout. So my weight stays the same, and my dress size stays the same. 🙁 I do 30 minutes of weight training and other muscle exercises 2-4 times a week depending on my schedule.

  10. Victoria Hi….have you tried doing rampantly less weights ? I know it sounds counter-intuitive (read Myers wonderful book Intuition its powers and perils) but i would think you’d be suprised.
    Our genome isn’t adpated to rote repeticious steady state activities.
    ‘Ope of use

  11. I recently read “The Rosedale Diet” and Rosedale recommends less protein than you do (.5 g protein/ lb lean body mass, add 10 g protein “if you are a heavy exerciser”). He also seems to believe that excess consumed protein will be turned into sugar, which in turn is converted to excess fat. On the other hand, you state that “dietary protein turning to fat is not something we really need to worry about”.
    Is this a point on which reasonable people can disagree or do you think Rosedale is pretty much wrong?
    Hi Imsovain–
    Rosedale and I have a difference of opinion on the issue I suppose. In fact he and I are going to debate the how-much-protein-is-enough issue in a public forum at the American Society of Bariatric Physicians national meeting this October in San Diego. I’ll keep you posted as I put together my material because the issue isn’t a simple one that can be explained in a sentence or two. And there is a big difference in how much protein is required on a low-carb diet verses a high-carb diet.

  12. By the way, what’s up with Dr. Rosedale’s lack of a web presence? I ask because you mention him in PPLP. He has a website, but it only seems accessible by password. Is he too busy with real patients? Was he besieged by annoying questions by random people on the Internet like me? Did he not get enough business from his website to justify his time? Nosy people want to know!
    I haven’t spoken with Dr. Rosedale for about a year and a half. I don’t have a clue as to what’s happening with his website, or to him, for that matter. He and I are going to debate optimal protein intake at a medical meeting in San Diego in October. I’m sure we’ll get together for dinner or something while we’re there and catch up. I’ll keep you posted.

  13. Hello, I have a question that is a follow-up to one of your responses posted on 6/21/06 above: You stated that, “One of the problems with insulin resistance is that elevated levels of insulin convert estrogen into testosterone in women. Were they to lower their insulin levels, which is easily done with a low-carb diet, they wouldn’t have nearly as much free testosterone to worry about.” This statement contradicts my understanding that low carb dieting helps to keep testosterone levels higher, and that extreme low fat diets tend to cause T levels to plummet. Are you applying this statement to women only? As a male who is starting his middle age years, I am trying to keep my T levels as high as possible naturally, and I have read that low carb is one of the best ways to do so. Your thoughts are appreciated.
    Hi Michael–
    Thanks for the question–I should have been a little clearer. As far as sex hormones are concerned, elevated insulin levels cause different in men than is women. In women, as I mentioned, hyperinsulinemia tends to convert estrogen to testosterone, which is why many obese women, especially obese women with PCS, are often masculinized. They sometimes develop facial hair and male pattern baldness. In men hyperinsulinemia causes the testosterone to convert to estrogen, which is why many obese men develop breasts, decreased facial hair, and other feminine characteristics. Body builders have a problem with this because they often want elevated insulin levels to pack on the muscle and end up with breasts. You are on the right track with a low-carb diet; it will ensure that you will get maximum benefit from all your own testosterone.
    Hope this answers your question.

  14. the testosterone “thing” has been a BIG deal with nay-sayers of low-carbing.
    I AM the best of examples. I feel stronger afer a long, hard bike ride than before. My sex-drive is pronouncely better.
    For those of you out there with Bodybuilding concerns, I want to tell you this.
    I was always able to build muscle through workouts my whole life.
    A few years ago, I was diagnosed with type II and hypothyroid.
    After reading Protein Power, I went full-bore with high protein/fats and low-to-zero carbs.
    EVERYTHING changed for the better. My muscle tone is awesome: arms – 20.5″, chest 51″, wear 36-38 pants (depending on leg cut). Strength is BEST with strictest carb-intake.
    Every once in a while, I eat some carbs because I want to. Always feel worse for it.
    I can ride a bike for many, many miles WITHOUT EATING a thing and ingest only water and feel great. In fact, soon as I eat something, strength/energy level goes DOWN immediately after.
    I cannot believe that I am unique or some sort of aberation.
    One advice: IF you eat lots of carbs one day, do the following:
    1- WORKOUT the next morning on empty stomach – after sluggish start, you will feel great.
    2- Eat later in day: PROTEIN/FATS only.
    From the Lab that is my body,
    Hi Gil–
    Thanks for the dietary and workout history. I’m glad you’ve found what works best for you. Keep after it.

  15. one more thing:
    Want to make it clear that I have never taken anything
    even remotely resembling “hormones or their precursors”.
    Though I have an innate ability (probably low myostatin)
    to build muscle it is besides the point that I feel better,
    have more muscle and much, much better energy etc…
    Thanks for the addendum.

  16. “We get some sugar from the breakdown of fat, but not much. Triglycerides, i.e., stored fat, are made of three fatty acids attached to a glycerol backbone. When the fatty acids that we are burning for energy are stripped away from the glycerol, the liver converts these left-over glycerol molecules into glucose. Most of our sugar, however, comes from the breakdown of muscle tissue. The liver converts certain amino acids that make up muscle into sugar in a process called gluconeogenesis.” [Quote]
    So what is the amount of fat broken down for sugar dependent on? Assuming vlc/no carb & high fat intake?
    The amount of sugar that comes from the breakdown of fat is fairly small, maybe 10 percent of the total. But it’s dependent on only the breakdown of fat. If fat breaks down, the fatty acids are stripped from the glycerol backbone. This glycerol is then freed up to be used for conversion to glucose. It doesn’t matter whether th fat breakdown happens during low-carb dieting or low-fat dieting, the glycerol is released just the same. But more fat will be broken down during a low-carb diet, meaning that more glycerol will be released.

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