The Western world is in the midst of an obesity epidemic that has been worsening since the 1980s. Rates of related illnesses such as heart disease and diabetes are also rising, with type 2 diabetes affecting children at ever younger ages. Understandably, weight loss has become a national obsession. We’ve turned to dieting, counting calories, stocking up on “heart-healthy” frozen dinners, and churning away millions of hours on treadmills and exercise bicycles. Yet despite decades of expert advice to eat fewer calories, avoid fat, and exercise more, Americans keep getting more obese.

Where does that expert advice come from? The current scientific orthodoxy in nutrition began in the middle of the 20th century, when prevailing medical opinion shifted toward two ideas. The first is that animal products—animal fat in particular—are harmful and should be minimized or eliminated from the diet. The other pillar of conventional wisdom is that obesity is a problem of energy balance: excessive fat accumulation results from some combination of overeating and a lack of physical activity.

These notions took root in the popular mind amid a climate of American self-criticism in the cultural ferment of the 1960s and 1970s. Vegetarianism came to be seen as more humane and environmentally conscious than a meat-based diet, and the idea that obesity and disease follow from over-consumption and sloth resonated as an echo of our moral failings. We drive our cars too much and don’t walk enough. Cheap food, like cheap goods and cheap pop culture, is consumed to mindless excess. Just as we despoil our culture and environment, we despoil our own bodies. Most of all, we’re lazy and refuse to control our appetites.

But to science journalist Gary Taubes the idea that successful weight loss depends on eating less and exercising more is a dangerous myth. In Why We Get Fat he argues that obesity is the result not of sloth, gluttony, or diets overly rich in calories and animal fats but comes instead from consuming too many carbohydrates, particularly from wheat flour and sugar. This is more than a diet book, however—it’s a tour of the history of nutritional science and a primer on the biology of fat accumulation. Taubes argues that carbohydrate-rich Western diets are implicated in a broad array of modern diseases, such as heart disease, stroke, diabetes, even cancer—an assortment once termed “diseases of civilization” because they are virtually unheard of in populations that have not come into contact with the products of agriculture.

Taubes flatly rejects what he terms “the calories-in/calories out idea” that sees fat tissue as a repository for extra calories. As a principle of weight loss, it doesn’t stand up: scientific investigation into reduced-calorie dieting and exercise has unfailingly shown these approaches fail to help people control their weight in the long term. The “calories-in/calories out idea” depends on a mistaken conception of how fat tissue operates, Taubes argues: “The evidence that fat tissue is carefully regulated, not just a garbage can where we dump whatever calories we don’t burn, is incontrovertible.”

He contends instead that obesity is caused by a simple chain of events. Consumption of carbohydrates triggers a rise in blood sugar. Elevated blood sugar leads the body to secrete insulin to store it, and excessive insulin, the body’s primary regulator of fat, drives fat accumulation. As Taubes writes:

[T]he science itself makes clear that hormones, enzymes, and growth factors regulate our fat tissue, just as they do everything else in the human body, and that we do not get fat because we overeat; we get fat because the carbohydrates in our diet make us fat. … obesity is ultimately the result of a hormonal imbalance, not a caloric one—specifically, the stimulation of insulin secretion caused by eating easily digestible, carbohydrate-rich foods…

Obesity is indeed associated with increased food intake and sedentary behavior, but conventional wisdom reverses cause and effect. If excess insulin triggers fat accumulation, the upshot is that an increased proportion of calories that would otherwise be available for the body to use as energy are diverted into fat storage. This translates into a higher caloric requirement that registers as hunger, overeating, and a sedentary lifestyle. Gluttony and sloth, Taubes argues, are the result, not the cause, of obesity.

This hypothesis resolves some apparent public-health paradoxes, like the high incidence of obesity among poorer peoples such as Pacific Islanders and Native Americans who subsist largely on cheap, modern foods, notably white flour. Indeed, obesity often coexists with malnutrition in impoverished populations. “Being fat,” Taubes notes, “is associated with poverty, not prosperity. … The poorer we are, the fatter we’re likely to be.”

The diet Taubes advocates can contain plenty of animal products and the attendant saturated fat. But isn’t it well known that saturated fat contributes to heart disease? Taubes maintains that the weight of the evidence actually points to carbohydrates, not fat, as the culprit.

If he’s right, mainstream nutritional advice from the mid-1970s onward has contributed to higher rates of obesity. Indeed, Taubes argues, the consensus view on obesity has inflicted inestimable harm on public health. The “obesity epidemic” that began in the 1980s arrived alongside pervasive government and medical-establishment warnings to reduce meat and saturated fat in the diet—advice the public evidently heeded, as consumers began to replace meat, eggs, and dairy products with grains, sugar, and vegetable oils.

How could nutritional orthodoxy be so wrong? The proximate cause was simply scientific malpractice, as Taubes documented in his earlier book Good Calories, Bad Calories. In the 1960s and 1970s, scientists began to turn toward the idea that dietary fat and cholesterol cause heart disease. They improperly drew firm conclusions from epidemiological studies rather than from controlled, double-blind trials. They also tended to ignore studies whose conclusions disagreed with their already established beliefs. The public was harmed most of all by scientists’ good intentions: with the health of the nation at stake, many experts, feeling pressed to act quickly, believed they couldn’t wait for conclusive proof of their hypotheses before disseminating new dietary recommendations.

Taubes is not alone in his criticisms. The constellation of dissenters aligned against the diet establishment are by no means monolithic in their views, but all share the same basic critique of mainstream nutrition advice and the standard American diet. The popular “paleolithic” diet and fitness movement agrees with Taubes’s view that the diets of our hunter-gatherer ancestors are a model of what humans are best adapted to eat. Rather than focusing like Taubes on the broad categories of nutrients such as fat and carbohydrates, however, paleo enthusiasts have a more detailed set of prohibitions and recommendations, such as restricting dairy and vegetable oils and favoring meat from pastured, rather than factory-farmed, animals. The Weston A. Price Foundation and sympathetic researchers, meanwhile, embrace traditional dietary practices culled from various post-agricultural societies as well, including the fermentation of grains and vegetables and consumption of dairy products from pasture-raised livestock.

These overlapping schools of thought can be conceived of as a type of food traditionalism. They share a skepticism of medical-establishment and governmental recommendations on nutrition and a rejection of the factory-manufactured foods that line grocery-store aisles. The label of “food traditionalist” might not fit Gary Taubes as well as others in the movement who embrace a more holistic view of diet than his seemingly obsessive focus on macronutrients—fats, carbohydrates, and protein. But his value to this group is less his stringent emphasis on refined carbohydrates as the chief source of modern disease than his trenchant critique of the nutrition establishment’s recommendations.

Another figure who can be fairly described as a food traditionalist is Omnivore’s Dilemma author Michael Pollan, though he is less enamored with animal products than the paleo community is. Pollan’s mantra “Eat food, not too much, mostly plants” clashes with Taubes’s pro-fat proselytizing, and in In Defense of Food, Pollan criticizes what he terms Taubes’s “nutritionism,” the reductionist tendency to believe that “food is foremost about promoting physical health” and “that the nutrients in food should be divided into the healthy ones and the unhealthy ones—good nutrients and bad.” Nevertheless, Pollan praises Taubes for his work debunking orthodox views about fat, calling Taubes “The closest thing to … a scientific Aleksandr Solzhenitsyn to show up and expose the whole fat paradigm as a historical disaster.”

Food traditionalists can be found everywhere on the political spectrum, from leftist ex-vegetarians to localist libertarians. What they have in common is a rejection of the mass-produced output of industrialized agriculture and an embrace of older kinds of diet. They are also united in their opposition to what could be termed a food-medical-industrial complex of agricultural corporations, the medical and pharmaceutical industries, industry-connected organizations like the American Heart Association, and government agencies. The modern landscape of chronic, preventable disease is a disaster for the public, but a boon for many of these groups, which profit handsomely when Americans eat manufactured foods and develop chronic diseases that cost billions to manage, but which modern medicine is powerless to cure. Gary Taubes and other food traditionalists suggest an alternative to expensive and dangerous drugs and medical procedures—go back to what our forefathers wanted to eat.

Mark Nugent is a TAC senior editor.

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