HILDE BRUCH,
LET’S ASK A FEW MORE SIMPLE QUESTIONS about the nature of obesity and weight regulation. Even if we accept—just for the moment—that obesity is caused by a positive energy balance and thus some combination of overeating and sedentary behavior, why would anyone willingly continue to overeat or remain sedentary if obesity is the undesirable state it certainly appears to be? Why would energy balance remain positive when there are so many compelling reasons and so much time to stop the process and maybe reverse it? If a positive energy balance can be turned into a negative energy balance with reasonable facility by exercise and calorie-restricted diets, why is it so difficult to lose weight?
This is the paradox that haunts a century of obesity research. As Marian Burros wrote in the
In 1983, Jules Hirsch of Rockefeller University framed this enigma in the form of two alternative hypotheses. One was the common belief “that obesity is the result of a willful descent into self-gratification.” The other was the “alternative hypothesis that there is something ‘biologic’ about obesity, some alteration of hormones, enzymes or other biochemical control systems which leads to obesity.” Because no such biologic abnormality had been unambiguously identified, Hirsch believed, “it is perhaps better to maintain the illusion that obesity is not an illness. It is more pleasant to believe that it is no more than an error of good judgment and that better judgments and choices will eventually lead” to a better outcome.
Here is another apparent contradiction: it may be true that, “for the vast majority of individuals, overweight and obesity result from excess calorie consumption and/or inadequate physical activity,” as the Surgeon General’s Office says, but it also seems that the accumulation of fat on humans and animals is determined to a large extent by factors that have little to do with how much we eat or exercise, that it has a biologic component.
The deposition of fat in men and women is distinctly different. Men tend to store fat above the waist—hence the beer belly—and women below it. Women put on fat in puberty, at least in the breasts and hips, and men lose it. Women gain weight (particularly fat) in pregnancy and after menopause. This suggests that sex hormones are involved, as much as or more than eating behavior and physical activity. “The energy conception can certainly not be applied to this realm,” as the German clinician Erich Grafe observed in 1933 about this anatomical distribution of fat deposits and how it differs by sex.
Fat, or lack of it, runs in families and even does so, noted the pediatrician-turned-psychiatrist Hilde Bruch in 1957, with such characteristic shapes or body types that “this similarity may be as striking as facial resemblance.” And if girth has a genetic component, then that means it is regulated by biological factors—perhaps tilted in one direction for those who gain weight easily, and tilted in another for those who don’t. “It is genetics, and not the environment, that accounts for a large proportion of the marked differences in individual body weight in our population today,” wrote the Rockefeller University molecular biologist Jeffrey Friedman in 2004. If obesity does have such a significant genetic factor—“equivalent to that of height, and greater than that of almost every other condition that has been studied,” according to Friedman—then how does this figure into the equation of overeating and sedentary behavior?
The same could be asked about metabolic or hormonal factors, which also contribute to excessive adiposity, as Jerome Knittle of Rockefeller University explained in 1976, when he testified before George McGovern’s Senate Select Committee on Nutrition and Human Needs. “Infants born to diabetic mothers are heavier at birth, are relatively fatter and have a higher rate of subsequent obesity than infants of non-diabetic mothers of equal gestational age,” Knittle said. But if these physiologic factors make for fatter babies and subsequently fatter adults, couldn’t the same be true for those of us without diabetic mothers, too?
Some of us simply seem predisposed, if not fated, to put on weight from infancy onward. Some of us lie further along what Friedman described as the distribution of adiposity than others. In the early 1940s, the Harvard psychologist William Sheldon was referring to what he called the “morphology” of body types when he commented, “It does not take a science to tell that no two human beings are identically alike.” According to Sheldon, every human body could be described by some combination of three basic physical types: ectomorphs, who tend to be long and lean; mesomorphs, who are broad and muscular; and endomorphs, who are round and fat. You could starve endomorphs, Sheldon said, and they might lose weight and even appear emaciated, “but they do not change into mesomorphs or ectomorphs any more than a starved mastiff will change into a spaniel or a collie. They become simply emaciated endormorphs.”
In 1977, when McGovern’s committee held a hearing on obesity, Oklahoma Senator Henry Bellmon captured this dilemma perfectly. The committee had spent the day listening to leading authorities discuss the cause and prevention of obesity, and the experience had left Bellmon confused. “I want to be sure we don’t oversimplify…,” Bellmon said. “We make it sound like there is no problem for those of us who are overweight except to push back from the table sooner. But I watched Senator [Robert] Dole in the Senate dining room, a double dip of ice cream, a piece of blueberry pie, meat and potatoes, yet he stays as lean as a west Kansas coyote. Some of the rest of us who live on lettuce, cottage cheese and Ry-Krisp don’t do nearly as well. Is there a difference in individuals as to how they utilize fuel?” The assembled experts acknowledged that they “constantly hear anecdotes of this type,” but said the research was ambiguous. In fact, the evidence was clear, but it was difficult to reconcile with the assembled experts’ preconceived notion—the dogma—that obesity is caused by gluttony and/or sloth.
Over the past century, numerous studies have addressed this issue of how much more easily some of us fatten than others. In these studies, volunteers are induced to overeat to considerable excess for months at a time. The most famous such study was conducted by the University of Vermont endocrinologist Ethan Sims beginning in the late 1960s. Sims first used students for his experiments, but found it difficult to get them to gain significant weight. He then used convicts at the Vermont State Prison, who initially raised their food consumption to four thousand calories a day. They gained a few pounds, but then their weights stabilized. So they ate five thousand calories a day, then seven thousand (five full meals a day), then ten thousand, while remaining sedentary.
There were “marked differences between individuals in ability to gain weight,” Sims reported. Of his eight subjects that went two hundred days on this mildly heroic regimen, two gained weight easily and six did not. One convict managed to gain less than ten pounds after thirty weeks of forced gluttony (going from 134 pounds to 143). When the experiment ended, all the subjects “lost weight readily,” Sims said, “with the same alacrity,” in fact, as that with which obese patents typically return to their usual weights after semi-starvation diets. Sims concluded that we’re all endowed with the ability to adopt our metabolism and energy expenditure “in response to both over- and undernutrition,” but some of us, as with any physiological trait, do it better than others.
Another overfeeding study, led by Claude Bouchard, who is now head of the Pennington Biomedical Research Center in Louisiana, was published in 1990. Bouchard and his colleagues overfed twenty-four young men—twelve pairs of identical twins—by a thousand calories a day, six days a week, for twelve weeks. The subsequent weight gain varied from nine to thirty pounds. The amount of body fat gained also varied by a factor of three. In 1999, James Levine from the Mayo Clinic reported that he had overfed sixteen healthy volunteers by a thousand calories a day, seven days a week, for eight weeks. The amount of fat these subjects managed to put on ranged from less
