Good Calories, Bad Calories

logic keeps taking us in circles.

We arrive at the same conclusion if we ask why semi-starvation diets fail to cure obesity reliably, inducing only short-term weight loss by creating a negative caloric balance. Again, there are two possibilities. The first is that the obese stay on the diet but the weight loss eventually stops or even reverses itself. If this is the case, then whatever physiological mechanism is at work may be the cause of the obesity as well. If so, obesity may be caused not by overeating, whatever that means, and sedentary behavior—i.e., by positive caloric balance—but by some more profound underlying disorder. Since a metabolic disorder is not an option in the overeating/ sedentary-behavior hypothesis (if it were, then we might be discussing the metabolic-disorder hypothesis), the only allowable answer is the second possibility: the obese lack the willpower to remain on the diet—a character defect.

The closer we look at the overeating hypothesis, the more counterintuitive its logic becomes. Consider a thought experiment. The subjects are two middle-aged men of similar height and age. One eats three thousand calories a day and is lean. The other eats three thousand calories a day and is obese. (The epidemiologic and metabolic studies of the past century make clear that we could find two such men with little difficulty.) Let’s cut the calorie intake of our obese subject in half and semi-starve him on fifteen hundred calories a day. He will lose weight, although, if Albert Stunkard’s 1959 analysis holds true, there’s only one chance in eight he’ll lose even as much as twenty pounds. Our lean subject will lose weight on this diet as well, as Keys demonstrated with his conscientious objectors in 1944. That’s what the law of energy conservation implies. But they would both be hungry continuously, making it likely they would fall off the diet given time. That’s what common sense, the history of obesity research, and the Carnegie, Minnesota, and Rockefeller experiments tell us. And after some amount of weight loss, their weight will plateau, because their metabolism and energy expenditure will adjust to this new level of calorie intake. “Eventually, calorie balance is re-established at a new (low) plateau of body weight and the calorie deficit is zero,” as Keys explained.

Our intuition is that our obese subject will lose more weight because he has more to lose, but we have little evidence to that effect, one way or the other. And yet, if both our obese and lean subjects fall off the diet and return to eating three thousand calories a day, the obese individual will return to obesity, perhaps even fatter than ever, and thus will satisfy our diagnostic criterion for a character defect; our lean subject will also put back the weight he lost, and perhaps a little more, but will still be lean, and will not have to think of himself as possessed of a perverted appetite or some other character defect.

The same conclusion will be reached if our obese subject undergoes bariatric surgery. “This procedure alters gastrointestinal anatomy to reduce caloric intake beyond what could be achieved volitionally,” explains Jeff Friedman of Rockefeller University in a recent issue of Nature Medicine. “Although people who undergo bariatric surgery lose a significant amount of weight, nearly all remain clinically obese.” We will now have two individuals of more similar size and weight, one of whom needs a surgically altered gastrointestinal tract to reduce calorie intake so much that he can stay at that weight, and the other who doesn’t and can eat to his heart’s content. Our surgical patient is perceived as defective in character, having had to rely on surgery to curb his appetite. Our naturally lean subject is not, despite the possession of an identical appetite. “The implication,” as Friedman noted, “is that something metabolically different about morbidly obese individuals results in obesity independently of their caloric intake.”

Whatever the accepted wisdom, making obesity a behavioral issue is endlessly problematic. “Theories that diseases are caused by mental states and can be cured by will power,” as Susan Sontag observed in her 1978 essay Illness as Metaphor, “are always an index of how much is not understood about the physical terrain of a disease.” This is certainly the case with obesity. One goal of any discussion of the cause of obesity must be a way to think about it that escapes the facile and circular reasoning of the overeating/sedentary- behavior hypothesis and permits us to proceed in a direction that leads to real progress, to find a way of discussing the condition, as the philosopher of science Thomas Kuhn might have put it, that allows for a “playable game.”

Obesity researchers over the last century have struggled with this dilemma, but they failed to escape it, which is the inevitable consequence of circular logic. Von Noorden, for instance, sought to absolve the obese of character defects by suggesting that weight was gained so imperceptibly as to go unnoticed. He inaugurated the practice, ubiquitous today, of enumerating the subtle ways in which excess calories creep into our diet, or fail to be expended in our sedentary lives. Two hundred calories a day, he suggested, the content of five pats of butter or twelve ounces of beer, could easily slip into the diet unobserved and result in a weight increase, by his calculation, of nearly seventeen pounds a year. “These 200 calories represent such a small amount of food,” he explained, “that neither eyesight nor appetite afford any indication of it, and therefore the person can say to the best of his knowledge that his food-supply has not been altered, although he has obviously become corpulent.” Any such claims that obesity is caused by the slow and imperceptible accumulation of excess calories inevitably serves to blame obesity on the behaviors of overeating and inactivity, while avoiding the explicit accusation of a character defect. Such explanations also beg the question of how the victim managed to make the transition from lean through overweight to obese without noticing and then choosing to reverse the process.

The hypothesis that the currently rising tide of obesity is caused by a toxic food environment, as Yale’s Kelly Brownell has proposed, is another example of an attempt to blame obesity on the behavior of overeating, even while sympathizing with the sufferers. “As long as we have the food environment we do,” says Brownell, “the epidemic of obesity is predictable, inevitable, and an understandable consequence.” That environment, in his view, is the fault of the food industry, aided and abetted by the makers of computer games and television shows that encourage sedentary entertainment. Following this argument, severely obese people have sued fast-food chains, the inventors of supersizing, which supposedly pushes extra calories on unsuspecting bargain-conscious Americans. “Our culture’s apparent obsession with ‘getting the best value’ may underlie the increased offering and selection of larger portions and the attendant risk of obesity,” as James Hill of the University of Colorado and his colleague John Peters of Procter & Gamble suggested in Science in 1998.

But if the environment is so toxic, as the Mayo Clinic diabetologist Russell Wilder asked seventy years ago, “why then do we not all grow fat?” After all, Wilder observed, “we continue to be protected against obesity, most of us, even though we hoodwink our appetite by various tricks, such as cocktails and wines with our meals. The whole artistry of cookery, in fact, is developed with the prime object of inducing us to eat more than we ought.” This brings us right back to the character issue. Some misbehave in this toxic environment and become obese. Some do not.^*84

Albert Stunkard and Jean Mayer are among those investigators who argued that it was wrong to blame obesity on character defects, and yet still failed to extricate themselves from the circular logic of the overeating/ sedentary-behavior hypothesis. In his 1959 analysis of semi-starvation diets, Stunkard wrote that obesity research went astray once investigators concluded that “excessive body fat results from an excess of caloric intake over caloric expenditure” and then enshrined this thinking as the dictum that “all obesity comes from overeating.” After that, wrote Stunkard, the physician’s job became nothing more than to explain that “semi-starvation reduces fat stores, to prescribe a diet for this purpose,” and then to sit by and await the result. “If the patient lost weight as predicted, this merely confirmed the comfortable feeling that treatment of obesity was really a pretty simple matter,” wrote Stunkard. “However, if, as so often happened, the patient failed to lose weight, he was dismissed as uncooperative or chastised as gluttonous.” Mayer also ridiculed the logic that obesity was caused by gluttony or whatever was meant by the term overeating. “Obesity,” he wrote in The Atlantic in 1955, “it is flatly stated, comes from eating too much and that is all there is to it. Any attempt to search for causes deeper than self-indulgence can only give support to patients already seeking every possible means to evade their own responsibility.”