Of all the dangerous ideas that health officials could have embraced while trying to understand why we get fat, they would have been hard-pressed to find one ultimately more damaging than calories-in/calories-out. That it reinforces what appears to be so obvious—obesity as the penalty for gluttony and sloth—is what makes it so alluring. But it’s misleading and misconceived onso many levels that it’s hard to imagine how it survived unscathed and virtually unchallenged for the last fifty years.
It has done incalculable harm. Not only is this thinking at least partly responsible for the ever-growing numbers of obese and overweight in the world—while directing attention away from the real reasons we get fat—but it has served to reinforce the perception that those who arefat have no one to blame but themselves. That eating less invariably fails as a cure for obesity is rarely perceived as the single most important reason to make us question our assumptions, as Hilde Bruch suggested half a century ago. Rather, it is taken as still more evidence that the overweight and obese are incapable of following a diet and eating in moderation. And it puts the blame for theirphysical condition squarely on their behavior, which couldn’t be further from the truth.
There has to be a reason, of course, why anyone would eat more calories than he or she expends, particularly since the penalty for doing so is to suffer the physical and emotional cruelties of obesity. There must be a defect involved somewhere; the question is where.
The logic of calories-in/calories-outallows only one acceptable answer to this question. The defect cannot lie in the body—perhaps, as the endocrinologist Edwin Astwood suggested half a century ago, in the “dozens of enzymes” and the “variety of hormones” that control how our bodies “turn what is eaten into fat”—because this would imply that something other than overeating was fundamentally responsible for making us fat. And that’s notallowed. So the problem must lie in the brain. And, more precisely, in behavior, which makes it an issue of character. Both eating too much and exercising too little, after all, are behaviors, not physiological states, a fact that’s even more obvious if we use the biblical terminology—gluttony and sloth.
The entire science of obesity, in effect, got caught up in the circular logic of thecalories-in/calories-out hypothesis, and it’s never been able to escape. Establishing the cause of obesity as something that has to happen when people get fat—take in more calories than they expend—prevents any legitimate answer to the question of why anyone would ever do such a thing. Or, at least, why they would do it if they weren’t driven to it by forces outside their control.
We have the sameproblem if we ask why diets fail. Why is it that obesity is so rarely, if ever, cured by what should be the simple act of eating less? If we suggest as an answer that fat people respond to food restriction just as fat animals do—they reduce their energy expenditure, while experiencing increased hunger (as Jeff Flier and Terry Maratos-Flier explained in Scientific American)—then we’ve opened up thepossibility that the same physiologic mechanism that drives obese individuals to hold on to their fat in the face of semi-starvation might have been the cause of their obesity in the first place. Again, that’s not allowed. So instead we blame the failure of the diet on the failure of the fat person to stay on it. It’s a failure of will, a lack of the necessary strength of character to do what leanpeople do and eat in moderation.
Once overeating is established as the fundamental cause of obesity, blaming behavior—and thus a lack of character and willpower—is the only acceptable explanation. It’s the only one thatdoesn’t lend itself to further meaningful research and so, perhaps, the identification of a defect more fundamental still that would explain why people would willingly overeat if...