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“are generally lean and lank, with very small limbs and narrow chests.”

2
The Elusive Benefits of Undereating
    In the early 1990s, the National Institutes of Health set out to investigate a few critical issues of women’s health. The result was the Women’s Health Initiative (WHI), a collection of studies that would cost in the neighborhood of a billion dollars. Among the questions that the researchers hoped to answer was whether low-fat diets actually prevent heart disease or cancer, at least in women. So they enrolled nearly fifty thousand women in a trial, chose twenty thousand at random, and instructed them to eat a low-fat diet, rich in fruits, vegetables, and fiber. These women were given regular counseling to motivate them to stay on the diet.
    One of the effects of this counseling, or maybe of the diet itself, is that the women also decided, consciously or unconsciously, to eat less. According to the WHI researchers, the women, on average, consumed 360 calories a day less on their diets than they did when they first agreed to participate. If we believe that obesity is caused by overeating, we might say that these women were “undereating” by 360 calories a day. They were eating almost 20 percent fewer calories than what public-health agencies tell us such women should be eating.
    The result? After eight years of such undereating, these women lost an average of
two pounds
each. And their average waist circumference—a measure of abdominal fat—
increased
.This suggests that whatever weight these women lost, if they did, was not fat but lean tissue—muscle. *
    How is such a thing possible? If our weight is really determined by the difference between the calories we consume and the calories we expend, these women should have slimmed down significantly. A pound of fat contains roughly thirty-five hundred calories’ worth of energy. If these women were really undereating by 360 calories every day, they should have lost more than two pounds of fat (seven thousand calories’ worth) in the first three weeks, and more than thirty-six pounds in the first year. † And these women had plenty of fat to lose. Almost half began the study obese; the great majority were at the very least overweight.
    One possibility, of course, is that the researchers failed miserably at assessing how much these women ate. Maybe the women deceived the investigators and themselves as well. Maybe they didn’t undereat by 360 calories a day. “We have no idea what these women were really eating because, like most people when asked about their diet, they lied about it,” as Michael Pollan suggested in
The New York Times
.
    Another possibility is that this reduction in calories, this multi-year exercise in undereating, just didn’t do what it was expected to do.
    Of all the reasons to question the idea that overeating causes obesity, the most obvious has always been the fact that undereating doesn’t cure it.
    Yes, it’s true: If you are stranded on a desert island and starved for months on end, you will waste away, whether you’re fat or thin to begin with. Even if you are just semi-starved, your fat will melt away, as will a good share of your muscle. Try the same prescription in the real world, though, and try to keep it up indefinitely—try to maintain the weight loss—and it works very rarely indeed, if at all.
    This should come as no surprise. As I suggested earlier, with the assistance of Hilde Bruch’s wisdom and experience, most of us who are fat spend much of our lives
trying
to eat less. If it doesn’t work when the motivation is merely decades of the intense negative reinforcement that accompanies obesity—social ostracism, physical impairment, increased rate of disease—can we really expect it to work just because an authority figure in a white coat insists that we give it a try? The fat person who has never tried to undereat is a rare bird. If you’re still fat, as Bruch noted, that’s a good reason to assume