EIGHT   THE PROOF IN THE LOW-FAT PUDDING

Whatever the sacrifice of pleasure, it would be made up for by better health—that, at least, has always been nutritionism’s promise. But it’s difficult to conclude that scientific eating has contributed to our health. As mentioned, the low-fat campaign coincided with a dramatic increase in the incidence of obesity and diabetes in America. You could blame this unfortunate fallout on us eaters for following the official advice to eat more low-fat food a little too avidly. This explanation suggests that the problem with the low-fat campaign has been in its execution rather than in the theory behind it, and that a better, clearer public health message might have saved us from ourselves. But it is also possible that the advice itself, to replace fats in the diet with carbohydrates, was misguided. As the Hu paper suggests, there is a growing body of evidence that shifting from fats to carbohydrates may lead to weight gain (as well as a host of other problems). This is counterintuitive, because fats contain nearly twice as many calories as carbs (9 per gram for fats as compared to 5 for either carbohydrates or protein). The theory is that refined carbohydrates interfere with insulin metabolism in ways that increase hunger and promote overeating and fat storage in the body. (Call it the carbohydrate hypothesis; it’s coming.)* If this is true, then there is no escaping the conclusion that the dietary advice enshrined not only in the McGovern “Goals” but also in the National Academy of Sciences report, the dietary guidelines of the American Heart Association and the American Cancer Society and the U.S. food pyramid bears direct responsibility for creating the public health crisis that now confronts us.

Even if we accept the epidemic of obesity and diabetes as the unintended consequence of the war against dietary fat—collateral damage, you might say—what about the intended consequence of that campaign: the reduction of heart disease? Here is where the low-fat campaigners have chosen to make their last stand, pointing proudly to the fact that after peaking in the late sixties, deaths from heart disease fell dramatically in America, a 50 percent decline since 1969. Cholesterol levels have also fallen. Epidemiologist Walter C. Willett of the Harvard School of Public Health (a coauthor of the Hu paper) cites the increase in consumption of polyunsaturated fats “as a major factor, if not the most important factor, in the decline in heart disease” observed in the seventies and eighties and calls the campaign to replace saturated fats in the diet one of the great public health success stories of our time. And so it would appear to be: We reduced our saturated fat intake, our cholesterol levels fell, and many fewer people dropped dead of heart attacks.

Whether the low-fat campaigners should take the credit for this achievement is doubtful, however. Reducing mortality from heart disease is not the same thing as reducing the incidence of heart disease, and there’s reason to question whether underlying rates of heart disease have greatly changed in the last thirty years, as they should have if changes in diet were so important. A ten-year study of heart disease mortality published in the New England Journal of Medicine in 1998 strongly suggests that most of the decline in deaths from heart disease is due not to changes in lifestyle, such as diet, but to improvements in medical care. (Though cessation of smoking has been important.) For while during the period under analysis, heart attack deaths declined substantially, hospital admissions for heart attack did not. Modern medicine is clearly saving more people suffering from heart disease, but it appears that we haven’t had nearly as much success eliminating the disease itself.