The article below is a portion of Chapter 12 from Gary Taubes’ book The Case For Keto, presented here with permission from the author and publisher. The book is set for publication on Dec. 29, 2020, and is available for pre-order here.
Given a choice between a hypothesis and an experience, go with the experience.
Since the heyday of the Atkins diet in the 1970s, authorities have refused to accept the notion that LCHF/ketogenic eating is safe. (And those that do promptly lose their standing as an authority by doing so.) They believe that the fat content in the foods we think we should eat instead of refined carbohydrates and sugar is too high, so arguably unnatural. Those of us who promote this way of eating can speculate that many hunter-gatherer populations lived on vaguely similar diets and perhaps even in a state of ketosis—the Inuit, pastoralists like the Maasai warriors in Kenya, Native Americans in the winter months—but we’re just speculating. The unusual aspect of these diets leads to legitimate questions about risks outweighing the benefits. This is as it should be. No matter how much weight people might lose, no matter how easily, the orthodox medical opinion remains that these diets will kill us prematurely. Generations of physicians, medical researchers, dietitians, and nutritionists have been taught to believe (as was I and probably you, too) that we know what a healthy diet is. We know it because this is what healthy people tend to eat. They eat fruits, vegetables, whole grains, pulses (legumes), such as lentils, peas, and beans—mostly plants and plenty of carbohydrates. They avoid red meat and processed meats, and the fats they eat tend to be unsaturated, from plant sources rather than animal. Any radical deviation from this way of eating, regardless of weight loss, according to the consensus of medical opinion, is likely to be unsustainable and ultimately to our detriment.
This is the reason the authorities convened annually by U.S. News & World Report to judge diets and tell us what to eat rank LCHF/ketogenic diets as among the least healthy imaginable, regardless of the copious research and clinical experience that now argues quite the opposite. This is why two of the more media-savvy proponents of conventionally healthy eating—David Katz, a physician formerly associated with Yale University, and the former New York Times columnist Mark Bittman, a best-selling cookbook author—thought it appropriate to suggest recently in New York magazine that losing weight on LCHF/ketogenic eating (let alone maintaining weight for a lifetime) was analogous to getting cholera, an often fatal, infectious diarrheal disease. “Not everything that causes weight loss or apparent metabolic improvement in the short term is a good idea,” they wrote. “Cholera, for instance, causes weight, blood sugar, and blood lipids to come down—that doesn’t mean you want it!”
Despite the hyperbolic rhetoric, Katz and Bittman have our best interests in mind. Their concern is a legitimate one. The world is full of things we can do or take—medications and performance-enhancing substances—that will reverse and maybe even correct some symptoms of ill health in the short run, but will shorten our lives or ruin them if we take them for years or decades. The first rule of medicine is not actually to do well by your patient, but to do no harm. That’s the Hippocratic Oath. As a recent New York Times op-ed said about a drug that seems to do a remarkable job of quickly easing serious suicidal depression, “questions also remain about the safety of long-term use.”
Questions will always remain about the safety of long-term use … of anything. Imagine that you decide to take up running as a hedge against aging. Whether you think about it this way or not, you are implicitly making a judgment about the risks and benefits of the endeavor. Would you suffer more or less damage to your joints, for instance? Will you live longer by stressing your system in these workouts, or will they kill you prematurely? Marathoners die of heart attacks, too, occasionally young. Jim Fixx, author of The Complete Book of Running, a best seller in 1977, tragically died of a heart attack while out for a run. He was fifty-two years old. The conventional wisdom is that there are few things we can do that would be better for us, but we’ll never know for sure. We know that endurance runners seem to be very healthy, but that may not apply to us.
An almost universal misconception about nutrition and modern medicine—one shared by authority figures, physicians, and the journalists who cover the field—involves when clinical trials are necessary to guide our decisions and when they’re not. You do not need a clinical trial (costing tens of millions of dollars with tens of thousands of subjects) to tell you whether LCHF/ketogenic eating, or any regimen from vegan to carnivore, will allow you to achieve significant weight loss easily, without hunger, and make you feel healthier than you did. You can try any of these diets yourself and find out. It doesn’t matter what clinical trials conclude. What matters is what happens to you. Try changing the way you eat, and you will find out, just as you can take a new prescription drug and learn relatively quickly whether it helps whatever ails you and makes you feel better. Clinical trials are necessary to tell us about the long-term risks and benefits of one way of eating versus another—vegan, say, compared to carnivore, the two extremes—not the short-term. Those we can learn about reliably on our own.
“Is it safe?” is always one of two ultimate questions when considering a change of diet or lifestyle, particularly with the goal of preventing chronic disease. “Does it fix what ails us?” is the other. The two questions are so intimately related that we cannot discuss one without the other.
This is one of the many conspicuous problems with the argument that LCHF/ketogenic eating is simply too risky, if not for the short term, then for the long. The authorities who make this argument assume, as we’ve discussed, that we have viable alternatives, that we can achieve and maintain a healthy weight via any number of dietary approaches (so long as we eat less), like the Mediterranean diet, which they assume to be safe. For them, the observation that lean, healthy people eat this way—not all of them, though—seals the deal. To believe that it applies to all of us, you have to believe that those of us who fatten easily, as I’ve discussed and disagreed with strongly, are no different from those lean folks physiologically and hormonally.
By this orthodox thinking, LCHF/ketogenic eating is just another of many routes to doing what’s necessary: restricting calories and eating less. It’s seen as a particularly radical way to accomplish that, and radical ways to do anything are unnatural and entail, by definition, considerable risk, hence a relatively high likelihood of doing harm. According to orthodox thinking, eating a conventionally healthy diet as lean and healthy people appear to do, but less of it, is clearly an alternative for heavy people, one they can assume to be safe. These authorities simply will not confront the possibility that eating less or not too much of a conventionally healthy diet will not fix what ails many of us. If eating a conventionally healthy diet but less of it, and achieving and maintaining a healthy weight by doing so, is not a viable reality for us, then this argument falls apart.
It’s also critically important to understand the basis of the faith upholding these arguments. The authorities who make them—whether they are the experts convened for U.S. News & World Report or the U.S. Department of Agriculture’s dietary guidelines or the Katzes and Bittmans of the world or the well-meaning friends (“dude!”) who advise us to ease off the bacon—derive their opinions not from experience but from theoretical concepts about a healthy diet. They have merely embraced, as virtually all of us once did, the conventional hypotheses about the nature of a healthy diet. This way of thinking seems intuitively obvious and seems to work for them. In this sense, it’s helpful to think of the half-century-old controversy about the nature of a healthy diet as a conflict between hypothesis and experience. (I owe this way of thinking about the diet-health conflict to Martin Andreae, a physician in British Columbia, who made this observation when I interviewed him in the fall of 2017.)
On the one hand, we have ideas about how best to eat to be healthy, ideas we think are true or that seem to be true. On the other, we have what physicians observe in their clinics and what happens to us, what we experience, when we try different diets. The conventional wisdom on nutrition is dominated by the hypothesis that saturated fats cause heart attacks by raising cholesterol levels, specifically the “bad cholesterol” in low- density lipoproteins (LDLs). This hypothesis has dominated orthodox thinking on diet and health, much as the one ring in J. R. R. Tolkien’s The Lord of the Rings “rules them all.” Hence, eating polyunsaturated fats from corn, soy, or canola oil, instead of saturated fats, by implication, will make us live longer. The ideas that we should avoid animal products (red meat, eggs, and dairy in particular), that they do us harm, and that we will live longer and healthier lives if we eat a mostly or all-plant diet are also based largely on the fear of saturated fats.
Physicians and dietitians are expected to base their diet and lifestyle advice on these hypotheses, but they have no way to know whether their advice makes a difference. When a patient dies, as all eventually will, regardless of age or cause of death, regardless of whether her cholesterol levels changed or not, the physician is privy to no information about what role the low-fat diet might have played. By the same token, should I die tomorrow or in my hundredth year, my next of kin will not know if my unconventional high-fat eating shortened my life or lengthened it. (Critics of my nutrition work will insist that the fat killed me prematurely, regardless, but they’ll be guessing.) Maybe Jim Fixx would have had his tragic fatal heart attack a decade younger had he not taken up running. Maybe he would have died in his early fifties regardless. We’ll never know.
Even if we had strong clinical trial evidence to support these hypotheses, which we don’t, we wouldn’t know the answer to these questions. The hypotheses and the evidence on which the authorities come to these conclusions—i.e., to embrace these assumptions—suggest only that we’re more likely to live longer if we eat conventionally healthy diets and exercise, not that we will. So we will have to make a risk-benefit analysis as to whether the likelihood that we’ll live longer makes it worth engaging in the relevant behavior for the rest of our lives. This raises another obvious question: If the authorities are right, for instance, that eating saturated fat will shorten our lives, can we quantify it? How much longer can we expect to live if we restrict our fat consumption?
This is yet another question the authorities seem to avoid, perhaps because the answer is not to their liking. If the conventional wisdom is right and eating saturated fat raises your LDL cholesterol (as for many of us it will) and so gives you a heart attack and kills you prematurely, how many years of life would you have gained if you avoided fat-rich foods and particularly those with saturated fat, or replaced at least some of that saturated fat (from animals) with polyunsaturated fats from seed oils, as the authorities concerned with our heart health advise? In other words, assuming the experts are right, what kind of culinary sacrifice is our fear of saturated fat worth?
As I noted in my 2002 New York Times Magazine article, the answer to that question was worked out long ago by three groups of researchers, all in agreement: at Harvard (published in 1987), at McGill University in Montreal, and at the University of California San Francisco (both 1994). These researchers estimated the benefit to longevity if we cut our fat consumption by a quarter and our saturated fat consumption by a third from what we might have typically eaten back then, lowering our cholesterol significantly, and they all concluded that absent other serious risk factors for heart disease, we’d live on average from a few days to a few months longer.
As one of these researchers pointed out to me when I interviewed him, the added time is not in the prime of our lives but rather at the very end of our lives. This seems obvious, but it’s a point worth pondering. Instead of dying, say, in March of our seventy-fifth year, we die in April or May. A ninety-year-old is likely to get a few more months being ninety or maybe will make it to ninety-one. That could be a good thing when you’re ninety, or maybe not, depending on the quality of your life at the time. A sixty-year-old is likely to gain only a couple of extra weeks. It’s not even clear that this dietary intervention prevents any heart attacks. Even in the best of all worlds, it may delay them merely by those few weeks or months.
After the 1987 Harvard analysis was published in the Annals of Internal Medicine, Marshall Becker, a professor of public health at the University of Michigan, suggested that avoiding fat or saturated fat to prevent heart disease is “analogous to stewards rearranging the deck chairs on the Titanic.” Even that analogy, though, assumes that all the fat-restricted diet does is prevent heart disease and doesn’t do us harm—for instance, make us fatter and more diabetic because of its carbohydrate content.
There is another way to parse these statistics of population averages, and this is the one the authorities seem to prefer. It is indeed possible that a few of us will die prematurely, perhaps at fifty instead of eighty, as a direct result of elevated cholesterol. If those people eat a cholesterol-lowering diet, they will live significantly longer. But they don’t know who they are in advance—nobody does—so we all have to eat the cholesterol-lowering diet for those lucky people to benefit. The rest of us would get no benefit at all. We may even be harmed by such a diet, as many doctors now believe. In 1999 one of the legendary experts in cholesterol research, Scott Grundy of the University of Texas, described this to me as the I-have-to-eat-a-low-fat-diet-for-life-so-my-neighbor-down-the-street-doesn’t-get-a-heart-attack scenario. Ninety-nine out of one hundred of us who avoid butter and bacon for a lifetime may well do it for no health benefit whatsoever, even if the conventional wisdom on saturated fat is right.
Physicians who embrace and prescribe LCHF/ketogenic eating believe that these conventional healthy-diet hypotheses are refuted daily in their lives and in their practices. After all, many of them and their patients had lived and eaten by these conventional guidelines while they got progressively fatter and sicker (as had I). Some had been vegetarians, even vegans, but LCHF/ketogenic eating was what eventually allowed them to easily lose their excess fat and reverse any progression toward hypertension or diabetes. That’s what they directly observed, and that, in turn, is what their patients experience. No faith is necessary to observe or experience these benefits.
Recall what the hundred-plus Canadian physicians wrote in HuffPost about their observations, their experiences, when their patients embraced LCHF/ketogenic eating: “What we see in our clinics: blood sugar values go down, blood pressure drops, chronic pain decreases or disappears, lipid profiles improve, inflammatory markers improve, energy increases, weight decreases, sleep is improved, IBS [irritable bowel syndrome] symptoms are lessened, etc. Medication is adjusted downward, or even eliminated, which reduces the side-effects for patients and the costs to society. The results we achieve with our patients are impressive and durable.” Physicians who now prescribe these diets commonly say that they rarely if ever prescribe drugs to their patients for blood sugar control or hypertension; rather, they de-prescribe, they get patients off medications. That’s compelling testimony.
One physician I interviewed put this trade-off in perhaps its starkest perspective. Caroline Richardson is a family medicine doctor at the University of Michigan and a health services researcher who also works for the university’s Institute for Healthcare Policy and Innovation. She started her career doing physical activity research and then gradually transitioned into diabetes prevention. For years, she told me, she counseled her patients to follow the Diabetes Prevention Program regimen of low-fat, calorie-restricted diets plus exercise. Most of her patients, though, were extremely obese and half were diabetic. Slowly she shifted into studying and prescribing LCHF/ketogenic eating—typically, after finding out how well a relatively low-carb diet worked for her.
Now Richardson tells her patients to read Always Hungry?: Conquer Cravings, Retrain Your Fat Cells, and Lose Weight Permanently by David Ludwig, a physician and professor of nutrition at Harvard, and to study its low-carb recipes. “One thing I love about the low-carb, high-fat diet, which I say again and again to my patients, is it makes you feel better.” The situation is similar to that of exercising, she told me. She advises her patients to exercise not because they’ll be healthier five years from now. She suggests they do it because they’ll feel better now. “When my patients cut out the carbohydrates, every single one comes back saying, ‘Wow, I feel like a new person.’ And one thing my patients tell me all the time is, ‘I don’t care if I die in ten years, I feel like crap today, I want to stop feeling like crap today.’”
Dan Murtagh’s take on this trade-off is also worth hearing. Murtagh is a general practitioner working in Northern Ireland with a patient population of mostly middle- and working-class families. He told me that when he was in medical school—he graduated in 2002—he heard little discussion about an obesity or diabetes epidemic. By the time we spoke fifteen years later, he was diagnosing a new case of type 2 diabetes in his clinical practice weekly. He became interested in diet and nutrition in 2009 when a patient asked him about the safety and efficacy of a paleo diet. Murtagh did his homework and went “down the rabbit hole.” First he read The Paleo Diet by Loren Cordain, the Colorado State University exercise physiologist who did the formative thinking on this way of eating. That led Murtagh to books on LCHF/ketogenic eating. He says the arguments in these books (including mine) made sense to him, so he experimented on himself and then tried it on his patients. “It’s all very well waxing on about what you think is going to happen on these diets,” he said to me, “but eventually you have to roll up your sleeves and get to work and see what happens.”
When I interviewed Murtagh, he told me about several patients whom he had counseled to avoid carbohydrates and to replace those calories with natural (vintage) fats. About one diabetic patient, “not particularly heavy-set,” he said, “I don’t think remission is a strong enough word for what happened to his diabetes.” He described another patient, in his early fifties, as “textbook obese”: six foot one, 320 pounds, on his way to becoming diabetic, but already with fatty liver disease, gout, and hypertension. Prior to changing how he ate, this patient was taking two medications daily for his blood pressure, another medication for his gout, and another for chronic indigestion and heartburn. After a year of LCHF/ketogenic eating, he had lost upward of 110 pounds and was medication-free.
Surely he was healthier, but Murtagh’s medical colleagues who were still bound to the conventional thinking were not sanguine. “I discuss the same patients with them I’ve discussed with you,” he said, and he gets pushback. “I’m thinking, ‘Look, you’re telling me I should go back to this patient who’s lost 110 pounds and got off all his medications, and tell him to go back to eating his bread and cut the fat off his bacon.’”
The fact that LCHF/ketogenic eating produces such remarkable results in the clinic has always represented a tremendous challenge to the conventional thinking on nutrition. It creates an essential conflict, a cognitive dissonance, between two seemingly mutually exclusive definitions of what it means to “eat healthy.” Over the last fifty years, healthy eating has convention- ally been defined and institutionalized to mean eating fruits, vegetables, whole grains, and pulses in abundance, with plenty of carbohydrates—mostly plants—and minimal animal fats and little or no red or processed meats. The other definition is what many people appear to need to maintain a “healthy” weight: ideally little or no fruit, no whole grains, no legumes or pulses, very few carbohydrates, and plenty of fat, which often translates to plenty of red and even processed meat. How do we resolve the discrepancy? If achieving and maintaining a “healthy” weight requires us to eat an “unhealthy” diet, are we healthier or not?
Published December 29, 2020 by Alfred A. Knopf, an imprint of The Knopf Doubleday Publishing Group, a division of Penguin Random House LLC. Copyright © 2020 by Gary Taubes.
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