Weighing the Evidence Why We Get Fat: And What to Do Aboutit, Gary Taubes, Knopf, 272 pages
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 overconsumption 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 carbohydraterich 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. …