It’s not often that faculty members of major academic institutions do anything but sneer at low-carbohydrate diets. But that all changes now. Today brings the publication of a new book by a professor at Harvard Medical School, Dr. David Ludwig, on the virtues of low-carb dieting. As you can probably discern from the title, Always Hungry? Conquer Cravings, Retrain Your Fat Cells & Lose Weight Permanently, this book isn’t an academic treatise about some arcane aspect of carb restriction. It is, doubtless, the most comprehensive book on all facets of low-carb dieting published to date.
Dr. Ludwig starts his book with a brief description of the dietary struggles of Willam Taft, the 27th President of the United States. It is a story all too common for many of us.
In 1905, during his first term as secretary of war, William Taft weighed 314 pounds. On his doctor’s advice, Taft began a low-calorie/low-fat diet and exercise program, bearing striking similarity to standard weight loss treatment today. Soon, he reported feeling “continuously hungry.” At his presidential inauguration three years later, Taft weighed 354 pounds.
If you read the paper written about Taft’s efforts, you will see that from December 2 through December 24, 1905 he kept a meticulous handwritten tally of his daily weight. He ended up losing about 12 pounds over the 22 day period, while adhering to a draconian low-fat diet prescribed by his physician, showing that such a diet really can work for weight loss over the short term. But, as Taft’s ultimate result shows, the long term outlook is grim.
In an editorial published in the New York Times a year and a half ago, Dr. Ludwig details brilliantly why in the long run counting calories is doomed to failure.
Why is it so difficult to maintain a reduced calorie diet for any length of time? Because reducing calories, especially by reducing fat, leads to hunger, and hunger is hard to resist. Dr. Ludwig learned this both in his own life and in his experience with his many overweight patients.
Early in his career, Dr. Ludwig helped develop his hospital’s weight-loss clinic.
Like virtually all specialists at the time (and many to this day), our team … focused at first on calorie balance, instructing patients to “eat less and move more.” We prescribed a low-calorie/low-fat diet, regular physical activity, and behavioral methods to help people ignore hunger, resist cravings, and stick with the program. When they returned to the clinic, my patients usually claimed to have followed recommendations. But with few exceptions, they kept gaining weight — a depressing experience for all.
At the same time Dr. Ludwig was working with patients in the clinic, he was also involved in research. He found that his own research, along with that of many others, “demonstrated a fundamental principle of the body’s weight-control systems:”
Impose a change in behavior (for example, by restricting food), and biology fights back (with increased hunger). Change biology, however, and behavior adapts naturally — suggesting a more effective approach to long-term weight management.[italics in the original]
He “began to realize just how little evidence there was to support the standard obesity treatment.”
As he writes,
Soon my entire perspective shifted. I began to see food as so much more than a delivery system for calories and nutrients. Although a bottle of cola and a handful of nuts may have the same calories, they certainly don’t have the same effects on metabolism. After every meal, hormones, chemical reactions, and even the activity of genes throughout the body change in radically different ways, all according to what we eat. These biological effects of food, quite apart from calorie content, could make all the difference between feeling persistently hungry or satisfied, between having low or robust energy, between weight gain or loss, and between a lifetime of chronic disease or one of good health. Instead of calorie counting, I began to think of diet in an entirely different way — according to how food affects our bodies and, ultimately, our fat cells. [italics in the original]
Let’s digress a little to discuss the difference between academic physicians/researchers and clinicians in private practice.
Academic researchers vs clinicians in private practice.
When I stumbled onto the low-carb diet as the most successful way to help my patients lose weight, I was in private practice. Just about every diet book author falls into that same category. We’ve all seen what works by working with our own patients.
When I was on all of the many book tours I’ve been on, doubtless the most common question I’ve been asked is: If your diet is so good, why don’t you do a study? Most people have no clue what is entailed in doing a study, so, from their perspective at least, the question is a reasonable one.
But studies aren’t that easy to do. First, they require a lot of money. Second, there is a lot of bureaucracy involved, i.e., submitting to institutional review boards and various other procedural issues. Third, there is no guarantee of your results ever seeing the light of day. Frankly, most private practice clinicians don’t have a clue about how to get a study published.
Academic physicians, such as Dr. Ludwig, are set up not only to take care of patients, but to do studies as well. In fact, it’s pretty much demanded of them. The university systems within which they work provide the framework and some of the funding for these studies.
So, unlike their private practice counterparts, academic physicians can do the studies to prove (or disprove) the effectiveness of different therapies and diets.
During his 20 years of experience teaching, researching, and treating patients at Harvard Medical School, Dr. Ludwig has “overseen dozens of diet studies, authored more than 100 peer-reviewed scientific articles, and cared for thousands of patients struggling with their weight.”
The result of this effort has led him to a couple of conclusions regarding what drives obesity.
Overeating hasn’t made our fat cells grow; our fat cells have been programmed to grow, and that has made us overeat.
What is the driver of fat cell overgrowth?
Insulin’s effects on calorie storage are so potent that we can consider it the ultimate fat cell fertilizer.[italics in the original]
Dr. Ludwig’s studies on diet and insulin
One of the terrific features of Always Hungry? is the number of studies showing the superiority of the low-carb diet that Dr. Ludwig discusses in detail. Most of these studies he and his colleagues have themselves performed, so you’re getting the direct information. Another feature of the book is the 22 pages of citations, which is catnip for me and other medial literature hounds. Pretty much anything published on low-carb dieting is listed.
I want to take just a few moments to hit the highpoints of a few of Dr. Ludwig’s studies.
One of my favorites is one published in JAMA in 2012 showing that the body doesn’t treat all calories consumed equally.
In a seven month feeding study, during which researchers provided all the food, 21 young adult subjects went through multiple dietary regimens. After the weight-loss (~25 pounds) and weight-stabilization phases, the subjects went on diets with the same number of calories, but different carb, protein and fat ratios. One month was a high-carb diet (60 percent carb), another was a moderate-carb diet (40 percent) and the other was a low-carb diet (10 percent). The goal was to see if there were any differences in the number of calories burned in each of these three phases. Since the ‘calories in’ were the same for all diets, the number of ‘calories burned’ should be the same. It didn’t turn out that way, though.
We found that the participants burned about 325 calories a day more on the low-carbohydrate compared to the high-carbohydrate diet. This difference is equivalent to about an hour of moderately vigorous activity, in effect without lifting a finger.
One of the reasons I like this study so much is that it confirms what I had speculated. I wrote a post a couple of years before this study and guessed (based on many years’ experience with a lot of patients) that the metabolic advantage of a low-carb diet would be in the range of 100-300 calories per day. It was nice to see that number validated.
A couple of the really exciting studies Dr. Ludwig performed had to do with the after effects of high-carb diets as compared to low-carb diets.
I’m going to quickly mention just a couple, but you can read about these in detail in Always Hungry?
Dr. Ludwig and team provided adolescent boys three different breakfasts, each with precisely the same number of calories. One breakfast was a highly processed carb breakfast, another was a minimally processed carb breakfast, and the last was an omelette and fruit.
Blood sugar levels initially tracked with both amount of carbohydrate and the degree of processing, which would be expected. More easily absorbed carbs would get into the blood more quickly. But four hours later, the blood sugar levels of the kids who ate the breakfast of highly processed carbs were lower than those who ate the intermediate carb meal and the omelette. So, quickly up and quickly down.
Are these results mere scientific curiosities? Changes in the emergency stress hormones suggest not. Adrenaline surged at four hours after the [highly processed carbs], but remained stable after the other meals, suggesting the brain had experienced a true metabolic crisis — signs of hypoglycemia — after the [highly processed carbs].
To me the most exciting aspect of this study was the next part.
The researchers gave the teens these same meals for lunch, then provided them with platters of tasty foods and allowed them to nosh on as much as they wanted for the rest of the afternoon. Of course, the research team carefully measured the number of calories consumed over the afternoon. What did they find? A huge caloric difference in intake depending upon what had been eaten previously. Those consuming the high-carb breakfast and lunch ate a whopping 650 calories more over the rest of the afternoon compared to those who had the omelettes and fruit.
Similar effects have been observed in more than a dozen studies by different research groups. If only a small fraction of this 650-calorie difference happened for the general public meal after meal, day after day, it could account for much of the increase in body weight since the 1970s, as consumption of highly processed carbohydrate soared.
The final study I want to touch on is one Dr. Ludwig’s group did showing what happens in the brain after consumption of corn syrup, a highly processed carbohydrate found in many, many processed foods.
Overweight males consumed two different milkshakes. One contained corn syrup and the other uncooked cornstarch, a carb, but a slow-acting one. Aside from those differences, the two milkshakes were exactly the same: they each contained an equal number of calories and had the same macronutrient composition. The sweetness of the shakes was kept the same by the addition of artificial sweetener. The study was double blind in that neither the staff nor the patients knew which shake was which.
As in the study mentioned above, blood sugar rose faster and higher after the corn-syrup laden shakes. And, in similar fashion, the blood sugar fell further, and those consuming these shakes reported greater hunger. What’s really interesting, though, is what happened when the researchers scanned the brains of these subjects.
We conducted brain imaging scans, using a technique called functional magnetic resonance imaging (fMRI). The scans detected one brain region, called the nucleus accumbens, that lit up like a laser after the fast-acting shake. The effect was so strong and consistent, it occurred in every one of our participants, providing strong statistical confidence in the results. The nucleus accumbens is considered ground zero for reward, craving and addiction — including alcohol, tobacco, and cocaine abuse. Activation of this brain region on a weight loss diet would erode will power, making that sticky bun exceedingly hard to resist.
Hunger is hard enough to fight under any circumstances, but once the nucleus accumbens joins in, it’s all over.
These are just brief examples of a few of the many fascinating studies Dr. Ludwig describes in his book.
He discusses the many studies showing the low-fat diet to be of limited value. He also writes about the many studies showing low-carb diets to be vastly more effective. He discusses at length the issue of chronic inflammation and how it affects the fat cells and, consequently, obesity.
Here is a short video in which Dr. Ludwig talks about why low-fat diets have been such failures.
I was delighted to see Dr. Ludwig delve into the idea that chronic inflammation adversely affects the hypothalamus, which is a current interest of mine. When scientists want to make a laboratory animal fat, they can easily do so by damaging its hypothalamus. I’ve thought for a long time that the hypothalamus might be the root of the problem of resistant obesity.
Most people, it seems, can chug along okay and eat pretty much anything they want until they become obese and develop insulin resistance and all the rest that goes along with it. I’ve always suspected the hypothalamus must somehow get damaged in this process, because after the damage is done, it is difficult to control obesity, especially without carb restriction.
Sleep, gut bugs, fructose, fetal programming and salt
Not only does Dr. Ludwig dive into the literature, much of which he wrote himself, on the dietary control of obesity, he also looks at the studies on how important sleep is in both preventing and treating obesity. And how the multitude of bugs in the gut play a role in our health. He also discusses how obesity and excess carb consumption can even affect infants in utero.
He talks about empty calories and how fructose fits into the obesity equation. You’ll probably be surprised at what he has to say.
Ditto for salt. He lays out all the latest research showing how salt intake relates to insulin resistance.
And this is just the scientific part of the book.
The solution to the obesity problem
In this section of his book, Dr. Ludwig lays out an encyclopedic plan to, as he says in the subtitle, conquer cravings, retrain your fat cells and help you lose weight permanently.
In my time, I have read a lot of diet books. In fact, I’ve written a lot of diet books. And I can tell you unequivocally that Always Hungry? is the most comprehensive one I’ve ever read. There is nothing I can find that Dr. Ludwig has left out. He has recipes, shopping lists, substitution tables, a guide for roasting nuts and seeds, a series of weekly prep worksheets, the list goes on and on. He even includes a section on how to stay on the program at an Italian restaurant, a Chinese restaurant, a Mexican restaurant, etc. etc. etc. as the King of Siam would say.
Lest you think I’m a PR guy paid to hype Dr. Ludwig’s book, I’ve got to confess that I do have a few minor quibbles with it. First, he is a little less embracing of saturated fat than I am. Whereas I welcome it with open arms, he is still a little stand offish. But he does lay out the studies on which he bases his opinion.
Second, he recommends a little less carb restriction than I typically do. But, as he admits, people can lose faster on a lower-carb diet. He just feels that although it takes a little longer with a slightly higher level of carbs, such a diet is much more user friendly. And a diet easier to stick to will probably help people hang in there better through the hard times.
Finally, Dr. Ludwig is much more taken with the idea of the glycemic index (GI) than I am. And the glycemic load (GL). I’ve always been of the opinion that the GI and GL are basically carb restriction tarted up so that it is more palatable to the academicians, most of whom can’t otherwise abide the thought of a low-carb diet. Given the studies Dr. Ludwig has done on the slower absorbing carbs, i.e., those that are low GI, I can see how those carbs would cause less of a problem. But, still, old prejudices die hard.
These tiny quibbles aside, and they really are tiny, I can’t think of a better book to read if you’re planning on starting a diet or restarting your diet. Or if you have a friend or family member who is struggling with weight, this is the best book you could give them.
I can’t recommend it highly enough.