Good Calories, Bad Calories

diabetes and other metabolic diseases,” Kahn wrote. “And who knows, they might also live longer too.” Diabetologists implicitly take the same tack whenever they discuss the need for their diabetic patients to “normalize” blood sugar, while recommending that this be accomplished primarily with “intensive insulin therapy” rather than restricting the carbohydrate content of their diets.

Another common approach today is to accept the chronic elevation of insulin, and so IGF, as a likely cause of chronic disease, but then assume that the hyperinsulinemia is caused by insulin resistance, which in turn is induced by a combination of high-fat, energy-dense, high-calorie diets, physical inactivity, and excess weight. By this logic, any research that implicates increased insulin activity in disease only confirms that too much food and too little exercise are the true banes of our existence. This approach is the one employed by those clinicians and public- health authorities who now acknowledge that hyperinsulinemia, insulin resistance, and the associated physiological abnormalities of metabolic syndrome are important risk factors for heart disease, but then blame the syndrome itself on excess weight or, if the patient happens to be lean, on physical inactivity. The guidelines from the National Cholesterol Education Program manage to merge both of the latter two approaches, by first enumerating the causes of metabolic syndrome as overweight, physical inactivity, and an “atherogenic diet”—defined as a diet high in saturated fat and calories—and then suggesting that “pharmacological modification of the associated risk factors” is the most effective treatment.

In this approach, high-calorie, high-fat diets and sedentary lifestyles are seen as the causes of all the diseases of civilization. The causal link in this chain from diet and lifestyle to disease is excess weight. “Weight sits like a spider at the center of an intricate, tangled web of health and disease,” as the Harvard epidemiologist Walter Willett has described it in Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. Or, as Jeremiah Stamler suggested back in 1961, about heart disease in particular, “Excess weight and the common American pattern of gain in weight from young adulthood into middle age are highly prevalent and serious risk factors…. The problem is not the severe, marked, huge, circus-type-of obesity, but rather the 25 or 40 pounds put on gradually over the years—the moderate, creeping obesity so common among middle- aged American men.”

That excess weight is accompanied by an elevated risk of chronic disease is a given. The questionable assumption is that it is an excess of calories of all types, and the dense calories of dietary fat in particular, combined with a relative lack of physical activity, that causes weight gain. In the prevailing wisdom, a simple caloric imbalance is the culprit: we get fat because we consume more calories than we expend.

The alternative is that excess weight and obesity, like all diseases of civilization, are caused by the singular hormonal effects of a diet rich in refined and easily digestible carbohydrates. The fattening of our adult years, after all, is not just associated with chronic diseases of civilization, it is a disease of civilization, and so it, too, may be a symptom of an underlying disorder. In this hypothesis, it is the quality of the calories consumed that regulates weight, and the quantity—more calories consumed than expended—is a secondary phenomenon. Whatever causes weight gain is at the heart of this tangled web, and that is the question we must now address.

Part Three

OBESITY AND THE REGULATION OF WEIGHT

How may the medical profession regain its proper role in the treatment of obesity? We can begin by looking at the situation as it exists and not as we would like it to be…If we do not feel obliged to excuse our failures we may be able to investigate them.

ALBERT STUNKARD AND MAVIS MCCLAREN-HUME, in “The results of treatment for Obesity: A Review of the Literature and Report of a Series,” 1959

To cultivate the faculty of observation must then be the first duty of those who would excel in any scientific pursuit, and to none is this study more necessary than to the student of medicine. Without the habit of correct observation, no one can ever excel or be successful in his profession. Observation does not consist in the mere habitual sight of objects—in a kind of vague looking-on, so to speak—but in the power of comparing the known with the unknown, of contrasting the similar and dissimilar, in justly appreciating the connection between cause and effect, the sequence of events and in estimating at their correct value established facts.

THOMAS HAWKES TANNER, A Manual of Clinical Medicine and Physical Diagnosis, 1869

Chapter Fourteen

THE MYTHOLOGY OF OBESITY

A colleague once defined an academic discipline as a group of scholars who had agreed not to ask certain embarrassing questions about key assumptions.

MARK NATHAN COHEN, Health and the Rise of Civilization, 1989

CRITICAL TO THE SUCCESS OF any scientific enterprise is the ability to make accurate and unbiased observations. “To have our first idea of things, we must see those things,” is how Claude Bernard explained this in 1865; “to have an idea about a natural phenomenon, we must, first of all, observe it…. All human knowledge is limited to working back from observed effects to their cause.” But if the initial observations are incorrect or incomplete, then we will distort what it is we’re trying to explain. If we make the observations with preconceived notions of what the truth is, if we believe we know the cause before we observe the effect, we will almost assuredly see what we want to see, which is not the same as seeing things clearly.

The trouble with the science of obesity as it has been practiced for the last sixty years is that it begins with a hypothesis—that “overweight and obesity result from excess calorie consumption and/or inadequate physical activity,” as the Surgeon General’s Office recently phrased it—and then tries and fails to explain the evidence and the observations. The hypothesis nonetheless has come to be perceived as indisputable, a fact of life or perhaps the laws of physics, and its copious contradictions with the actual observations are considered irrelevant to the question of its validity. Fat people are fat because they eat too much or exercise too little, and nothing more ultimately need be said.

The more closely we look at the evidence and at obesity itself, the more problematic the science becomes. Lean people will often insist that the secret to their success is eating in moderation, but many fat people insist that they eat no more than the lean—surprising as it seems, the evidence backs this up—and yet are fat nonetheless. As the National Academy of Sciences report Diet and Health phrased it, “Most studies comparing normal and overweight people suggest that those who are overweight eat fewer calories than those of normal weight.” Researchers and public-health officials nonetheless insist that obesity is caused by overeating,