The reason for this book is straightforward: despite the depth and certainty of our faith that saturated fat is the nutritional bane of our lives and that obesity is caused by overeating and sedentary behavior, there has always been copious evidence to suggest that those assumptions are incorrect, and that evidence is continuing to mount. “There is always an easy solution to every human problem,” H. L. Mencken once said—“neat, plausible, and wrong.” It is quite possible, despite all our faith to the contrary, that these concepts are such neat, plausible, and wrong solutions. Moreover, it’s also quite possible that the low-fat, high-carbohydrate diets we’ve been told to eat for the past thirty years are not only making us heavier but contributing to other chronic diseases as well.

Consider, for instance, that most reliable evidence suggests that Americans have indeed made a conscious effort to eat less fat, and particularly less saturated fat, since the 1960s. According to the USDA, we have been eating less red meat, fewer eggs, and more poultry and fish; our average fat intake has dropped from 45 percent of total calories to less than 35 percent, and National Institutes of Health surveys have documented a coincident fall in our cholesterol levels. Between 1976 and 1996, there was a 40-percent decline in hypertension in America, and a 28-percent decline in the number of individuals with chronically high cholesterol levels. But the evidence does not suggest that these decreases have improved our health. Heart-disease death rates have indeed dropped over those years. The risk of suffering a severe heart attack, what physicians call an acute myocardial infarction, may have diminished as well. But there is little evidence that the incidence of heart disease has declined, as would be expected if eating less fat made a difference. This was the conclusion, for instance, of a ten-year study of heart-disease mortality published in The New England Journal of Medicine in 1998, which suggested that the death rates are declining largely because doctors and emergency-medical-service personnel are treating the disease more successfully. American Heart Association statistics support this view: between 1979 and 2003, the number of inpatient medical procedures for heart disease increased 470 percent. In 2003 alone, more than a million Americans underwent cardiac catheterizations; more than a quarter-million had coronary-artery bypass surgery.

The percentage of Americans who smoke cigarettes has also dropped considerably over the years—from 33 percent of Americans over eighteen in 1979 to 25 percent fifteen years later. This should also have significantly reduced the incidence of heart disease. That it hasn’t, strongly suggests we’re doing something that counteracts the beneficial effect of giving up cigarettes. Indeed, if the last few decades were considered a test of the fat-cholesterol hypothesis of heart disease, the observation that the incidence of heart disease has not noticeably decreased could serve in any functioning scientific environment as compelling evidence that the hypothesis is wrong.