The message should be straightforward: Carbohydrate-rich foods are fattening. Or to complicate it slightly such that naturally lean people might more likely understand: For those of us who fatten and particularly those who fatten easily, it’s the carbohydrates that we eat—the quantity and the quality—that are responsible. The relevant mechanism appears to be simple, as well: Carbohydrate-rich foods—grains, starchy vegetables, and sugars—work to keep insulin elevated in our circulation, and that traps the fat we eat in our fat cells and inhibits the use of that fat for fuel.
That’s what the obesity research community should have been trying rigorously to resolve or refute for the past sixty years. That’s what I’m assuming is true because of the reasons and the evidence discussed. That’s what we have to keep in mind as we think about how to eat.
This simple truth about carbohydrates seems so hard to understand because we’ve been trapped in a context of naïve conventional wisdom—eat less or not too much, avoid fat and saturated fat, eat mostly plants—which in turn spawned the fad diet phenomenon I’ve discussed throughout. By relegating the reality of dealing with obesity and overweight to practicing physicians, the nutritional authorities almost guaranteed a future in which reality and the straightforward steps required to overcome obesity-related disorders would be hard to discern.
When these physicians wrote self-help books about what they had learned during their conversion experiences, books that contradicted the conventional low-fat, eat-less, mostly plant wisdom, they had to say something new, something different from the physicians turned authors who preceded them. That’s the nature of publishing. It’s hard to sell a diet book or website that advises people to eat precisely as others have advised in the past, although for the most part a large proportion of these books are merely minor variations on this theme.
With each new addition to the diet book literature, the focus of discussion narrowed to what the books added to the baseline advice, typically what we should eat to attain a healthy weight rather than the simple message about which foods are fattening (to us) and that we should avoid. Discussions of paleo versus keto versus South Beach versus the Zone or even versus Weight Watchers and Jenny Craig or the dietary vehicle of Oprah’s latest weight-loss achievement focused on the subtle ways these approaches differ rather than what they all have in common: the advice to avoid or mostly avoid, at the very least, refined grains and sugars. As diet guides struggle to give added value and find a new way to sell an old message—one that still desperately needs selling, offering to hone our health to some hypothetical fine edge or allow us to have the longest possible health span or even mind span (avoiding dementia and staying sharp as we age)—they verge further into the speculative, maybe-right-probably-wrong research literature and away from reliable knowledge.
The simple and reliable advice is the same as it has been for the better part of two hundred years. It dates back at least to Jean Anthelme Brillat-Savarin in 1825 and The Physiology of Taste, which has never been out of print, an accomplishment that very few nonfiction books can claim after nearly two centuries. Brillat-Savarin got it as right as anyone. He had his own conversion experience, just as fad diet book authors typically do, and he wrote about it. He spent thirty years struggling with his weight—he called his paunch his “redoubtable enemy”—and eventually came to what he considered an acceptable standoff. He did so only after digesting the message “of more than five hundred conversations” he had held with “dinner companions who were threatened or afflicted with obesity.” In every case, he wrote, the foods they craved were breads and starches and desserts.
As a consequence, Brillat-Savarin considered it indisputable that grains and starches were the principal cause of obesity*2—along with a genetic or biological predisposition to fatten easily, which not everybody has—and that sugar exacerbated the fattening process. He lived in a time, though, when sugar was still a luxury for the wealthy, and sugary beverages were exceedingly hard to come by, at least compared to their ubiquity a century later. So he focused his advice on starches and flour, assuming that abstinence from flour would imply abstinence from sugar, since sugars back then came predominantly in baked goods, pastries, and desserts.
Brillat-Savarin acknowledged that those who wished to reduce their weight needed something more than just the usual advice to “eat moderately” and “exercise as much as possible.” The only infallible system, he said, had to be diet, and that diet had to remove the cause of the excess body fat:
Of all medical prescriptions, diet is the most important, for it acts without cease day and night, waking and sleeping; it works anew at every meal, so that finally it influences each part of the individual. Now, an anti-fat diet is based on the commonest and most active cause of obesity, since, as it has already been clearly shown, it is only because of grains and starches that fatty congestion can occur, as much in man as in the animals; in regard to these latter, this effect is demonstrated every day under our very eyes, and plays a large part in the commerce of fattened beasts for our markets, and it can be deduced, as an exact consequence, that a more or less rigid abstinence from everything that is starchy or floury will lead to the lessening of weight.
Brillat-Savarin even went so far as to imagine his readers complaining that more or less rigid abstinence from everything that is starchy or floury meant no longer eating the foods they craved. In other words, his readers then might be much like readers now. “In a single word he [Brillat-Savarin] forbids us everything we most love,” he wrote, “those little white rolls from Limet, and Achard’s cakes, and those cookies…and a hundred other things made with flour and butter, with flour and sugar, with flour and sugar and eggs! He doesn’t even leave us potatoes, or macaroni! Who would have thought this of a lover of good food who seemed so pleasant?” Brillat-Savarin’s response was simple (although I’m bowdlerizing the translation for the more sensitive times in which we live): Then eat these foods and get fat and stay fat!
For many or most of us, this logic offers little or no escape, and as Brillat-Savarin said, the conclusion can still be deduced as an exact consequence. If carbohydrate-rich foods make us fat, then we have to deprive ourselves of the pleasure of their eating if we want to avoid this fate or possibly reverse it. But then, as Brillat-Savarin also noted, these restrictions left plenty to eat and as much of it as desired, which meant meals could be consumed that were still plenty tempting but not fattening.
In the early 1860s, a formerly obese London undertaker named William Banting published multiple editions of the first internationally best-selling diet book. They sold so widely and so well that in some nations the word for “diet” is still a variation on “banting.” Banting, too, had a conversion experience, and he discussed it. He, too, had struggled for decades with his weight before being convinced, in his case, by a London physician, to avoid sugars, starches, and grains, and thereafter he effortlessly slimmed down. The pamphlet he subsequently wrote triggered such an uproar that The Lancet, a British medical journal, wrote two editorials on the approach. The first one derided Banting for not being a physician himself and suggested he mind his own business. (I can relate.) The second, five months later, took a more balanced perspective and made the point that a “fair trial” was needed to ascertain if “the sugary and starchy elements of food be really the chief cause of undue corpulence.”
That’s the simple issue, as defined reliably by an editor of a medical journal 150-plus years ago. It’s not whether one diet somehow works better than another, or whether a calorie is a calorie (as this subject is often discussed and debated), or whether one diet generates a “metabolic advantage” compared to another. The issue is whether the sugary and starchy elements of the diet are the chief cause of undue corpulence—why we get fat. If they are, as textbook medicine has implied for fifty years, then those are the foods we can’t eat.
The implications are also relatively simple. The more carbohydrate-rich the food and the easier those carbohydrates are to digest, the greater the blood sugar and insulin response, and the more fattening they are likely to be. And the greater the sugar content, as Brillat-Savarin suggested, the more fattening.
While starches and flours are absorbed into our circulation primarily as the carbohydrate glucose, the stuff of blood sugar, the sugar in our diet (technically sucrose or high fructose syrups), the sweet stuff, has a different chemical composition and, for this reason, does its damage via a different mechanism. Sucrose is a molecule of glucose bonded to a molecule of another carbohydrate called fructose. Fructose is the sweetest of the carbohydrates, and it’s why sugar is as sweet as it is, and why fruits, containing a little sugar and a little fructose, are also sweet when ripe.*3 When we consume these sugars, the glucose enters the circulation, becomes blood sugar, and stimulates an insulin response, but the fructose mostly doesn’t. It’s metabolized first in the small intestine and then the liver. These organs, the liver particularly, are then tasked with the job of metabolizing an amount of fructose, day in and day out, which they are apparently ill-equipped to do.
Our livers would be easily capable of metabolizing the trickle of fructose that they would have encountered during the few million years that preceded the coming of agriculture about ten thousand years ago: a little sugar, a little fructose, seasonally, in fruits, bound up in fiber, slow to digest (and not necessarily ripe fruits at that). Our livers might have had to deal with the fructose from honey as well. After the twelfth century, depending on where our ancestors lived and their wealth, the trickle increased very slightly as refined sugar, now separated from the fiber that slowed its digestion and absorption, was first imported from the Middle East into Europe. Then the Industrial Revolution came about, and the beet sugar industry was launched to join the cane sugar industry, and the trickle turned into a flood. In the late 1970s, the corn refiners got into the game with high-fructose corn syrup, and the flood of sugar rose even higher; some variant of sugar was consumed in huge amounts daily by all, from breakfast to postdinner desserts, drinks, and snacks.
From the early years of the nineteenth century to the very tail end of the twentieth, average per capita sugar availability (how much the food industry makes available for our consumption) increased in the United States more than thirty-fold: from the sugar equivalent of a single twelve-ounce can of Coca-Cola every week to that of more than five cans every day, for everyone, from newborns to centenarians.
Like any device tasked to do a job it isn’t designed to do, the liver does a poor job of metabolizing this daily flood of fructose. Liver cells use as much of the fructose as they can to generate energy, but they convert the rest, the excess, to fat. Reasonably reliable research suggests that this fat is trapped in liver cells, leading to a condition known as nonalcoholic fatty liver disease, which is associated with obesity and diabetes and is also becoming an epidemic in the modern world. Some very good biochemists think that the backup of fat in these liver cells, whether temporary or chronic, is a likely initial cause of the insulin resistance we’ve been talking about and that we’re trying to prevent and/or reverse. In short, insulin resistance starts in the liver and then becomes systemic.
All this science is still speculative, as is the contention that sugar is uniquely addictive (although if you have either children or a sweet tooth, you likely don’t need a lot of science to accept it). When adolescents with fatty liver disease stop consuming added sugar (as in a trial funded by my nonprofit organization, the Nutrition Science Initiative, and published in the medical journal JAMA in January 2019), the fat in the liver tends to go away. This suggests that insulin resistance—in children, at least—would resolve along with it.
All the other carbohydrates in our diet—glucose, lactose (in milk), maltose (in beer), and others—work more or less directly to make us store fat by raising blood sugar and so stimulating insulin. Sugar does it both directly and indirectly: The glucose raises blood sugar and stimulates insulin secretion, the fructose overwhelms the liver and causes fatty liver and insulin resistance, so that we secrete ever more insulin to all those other carbohydrates.
Brillat-Savarin’s observation that sugar makes everything worse when it comes to getting fatter still holds. If there’s a primary evil in this nutrition story, it’s almost assuredly sugar, and learning to avoid it and still enjoy both life and eating is key. It may not return you to health and correct your weight; that’s likely to require Brillat-Savarin’s more or less rigid abstinence as well. But it is step one in preventing the problem from getting worse.
While I’m making the case for abstinence, it’s important to realize that it is not a panacea. It does not mean that anyone who is obese will become lean, only that they will very likely become leaner and healthier, and they will do so without hunger. Other hormones influence fat accumulation, sex hormones in particular, and they do not respond directly to what we eat (although they may indirectly). Insulin is the direct primary connection to our food. For many of us, we will have to minimize our insulin secretion to create and prolong that negative stimulus of insulin deficiency, to mobilize and burn more fat than we store, to achieve and maintain a healthy weight. More or less rigid abstinence will indeed be both necessary and ideal.
Ultimately, your success will depend on your commitment. While this may be said for every diet, the commitment here is not to living with hunger. Some who need to lose a dozen pounds to attain what they perceive as their ideal weight and health might do fine just by cutting back on the more obviously fattening foods and the carbohydrates they contain—for instance, sugary beverages, beer (“shun beer as if it were the plague,” wrote Brillat-Savarin), desserts, and sweet snacks. These folks will do fine eating slow carbs, with their complement of fiber to slow digestion and absorption and keep insulin levels low. Rigid abstinence will not be necessary for them.
For most of us who have struggled with our weight for years or decades, however, rigid abstinence would be ideal. Physicians who recommend LCHF/ketogenic eating say they will settle for the best their patients can do, but they believe that the benchmark for how healthy we can be comes only with rigid abstinence. The physicians who have worked with obese patients the longest and whose clinics have accumulated the most experience, like Eric Westman at Duke University, are adamant. “The word on the street,” says Westman, “is that I’m too strict. But maybe you have to be strict.”
At a recent diabetes conference in Aspen, Colorado, I had the opportunity to speak with a young woman who had participated in a diet trial that my nonprofit had supported at Stanford. She had been obese her whole life, she told me, and weighed 240 pounds at the start of the trial. She was randomized to be among those participants who would follow an LCHF/ketogenic eating plan for a year. For the first three months she practiced rigid abstinence and lost thirty pounds without the obsessive thoughts of food and the hunger that accompany calorie-restricted diets. (She had charted her weight on an app on her smartphone, and this is what she showed me.)
Then the Stanford researchers suggested that she and her fellow study participants who were assigned to LCHF/ketogenic eating could and maybe should go back to eating small portions of carbohydrate-rich foods that they specifically missed. The researchers were worried that if the diet was too restrictive, the subjects might fail to sustain it and would drop out of the trial. So this young woman went back to eating berries, which for many of us would be benign, but now she lost only five pounds over the next three months. At the six-month mark, again on the advice of the researchers, she added back a little more fruit and never lost another pound.
It’s certainly possible that her weight would have plateaued even without the berries and then the fruit; we can never know. But neither will she—and that’s the point. Had this young woman continued with rigid abstinence, she might have lost significantly more weight. If so, she might have decided that rigid abstinence was clearly worth the effort, and that a berry- and fruit-free life was eminently worth living. As self-help and management advice books will often say, setting a goal and committing to it are vitally important. Without the commitment, we never get to find out if the goal is achievable. By diluting the commitment and allowing us to compromise, we never know.
To abstain more or less rigidly from sugary, starchy, and floury foods means we have to change the way we think about how we eat, the foods we eat and don’t eat, and the effort we put into thinking about every meal. Like anything that requires discipline, however, it gets easier the longer we do it. In this case, we have an advantage over other similar lifelong interventions: By changing what we eat, we’re changing our physiology, the very fuel that our cells need to survive and generate energy, and that in turn should change the type of foods for which we hunger. As our bodies learn to burn fat exclusively for fuel, it’s fat we should begin to crave—the butter rather than the toast.
Temptations will never vanish. A sugary treat may not be any less seductive than it ever was. Sugar may always have the power to excite our taste buds (and our liver) and trigger cravings for more. But the key is to not succumb. As our bodies switch to burning fat for fuel, the ability to say no to sugary treats will be reinforced. Many foods with sugar in them will taste too sweet as our tastes change. This is commonly reported. We will also become more adept at and habituated to keeping our lives and our environments sufficiently sugar-free and so temptation-free. Successfully quitting any addiction means learning to make the source of the addiction unavailable, whenever possible. Success will require making a commitment to an objective and then being both patient and resolute in achieving it and maintaining it.
Many of the physicians I interviewed for this book spoke about their own health and approach to LCHF/ketogenic eating in addiction terms. Robert Cywes, a pediatric surgeon who now runs bariatric surgery and weight-control programs for adults and adolescents in Florida, said to me, “To cut to the chase, we are a carbohydrate substance abuse program, not a weight loss program.” Martin Andreae, a general practitioner in Powell River, Canada, just north of Vancouver, described himself as a reformed sugar addict.
“One brownie and I should be done,” Andreae said. “My common sense says stop there, but my actions don’t. I understand the feeling of addiction, the powerlessness of it. But the joy we get from an addiction is filling the void created by the absence of the substance itself. And you don’t cure an addiction with moderation; you do it with abstinence. Any other addiction field, that’s how we treat it. Alcohol: We say stop it altogether and don’t even have alcohol in the house. It’s the same with smoking. With diabetes and obesity, your body is essentially a sugar or carbohydrate addict. Telling our patients to moderate intake is telling them to do something that is almost physiologically impossible and keeps the addiction alive. What we’re fighting against is the concept of moderation. It doesn’t work.”
Mark Cucuzzella, a physician and professor of medicine at the West Virginia University School of Medicine, referred to himself in our interview as a “prediabetic in remission,” while implying that he is a carbohydrate addict in recovery. Cucuzzella is a marathoner, author of a book on running and health (Run for Your Life), and he eats and prescribes LCHF/ketogenic eating. His conversion experience was prompted by a diagnosis of prediabetes despite weighing only 135 pounds (he’s five foot eight) and religiously running ten miles a day. He says he was “literally” eating carbohydrates every three to four hours, including at two in the morning. He described his life, day and night, as “hungry, eat, hungry, eat, hungry eat….My last bowl of cereal and my last piece of bread were over six years ago. I do not miss them.”
Using language from Gretchen Rubin’s The Happiness Project, Cucuzzella divides his patients into “moderators” and “abstainers.” “A moderator can eat one little square of dark chocolate and walk away,” he says. “An abstainer has one bite, and it will not go well—he’ll eat the whole damn bar. One of the messages that has been a complete disaster for patients with obesity and diabetes is that we can do this in moderation. But if you’re really carb-addicted, telling you to go from ten doughnuts down to four is just telling you to think about eating the doughnuts all day. A rare patient can be a moderator when it comes to tasty carbs and succeed. Most of us need to be abstainers. Like people with alcoholism, drug addiction, and smoking, we need to avoid completely, and then we’ll have better odds of success. Why this advice is considered ‘extreme’ is beyond my comprehension as I witness patients daily who suffer from these metabolic diseases.”
*1 Thanks to Albert Einstein for this thought, although he was talking about scientific theories, not how to eat, and this is probably a simplification of what he actually said, not a direct quote.
*2 Brillat-Savarin was confusing association with causation here.
*3 High-fructose corn syrup, as we consume it most commonly, is a mixture of 55 percent fructose molecules and 40-plus percent glucose and a few other carbs thrown in as well. For our purposes, it’s just another version of sugar, so when I say sugar or sugars, I’m speaking of sucrose and high-fructose syrups.