But the trap that Stunkard and Mayer had identified is built into the logic of the positive-caloric-balance hypothesis; there is no escaping it. Mayer, as we’ve discussed, proceeded to insist in his book Overweight, as in all his writing, that obesity was the result of sedentary behavior, which simply implicated sloth rather than gluttony and still left the issue defined as a behavioral one. Although Mayer gets credit for convincing his peers that obesity has a genetic component, he implied that the only role of these genes was to make us want to be more or less sedentary. By the end of Overweight, Mayer was insisting not only that the obese must exercise more, but that they must also try harder to eat less. “Obesity is not a sin,” he wrote. “At most, it is the consequence of errors of omission, the result of not having kept up the life-long battle against an inherited predisposition and against an environment which combines constant exposure to food with the removal of any need to work for it physically. In the pilgrim’s progress of the constitutionally plump, salvation demands more than the shunning of temptation. It requires…the adoption of an attitude almost stoic in its asceticism and in the deliberate daily setting aside of time for what will be often lonely walking and exercising.”

Stunkard became a leading authority in the study of behavioral therapy for obesity, which can be defined as a system of behavioral techniques by which obese patients might come to endure semi-starvation, while avoiding the explicit judgment that they achieved their obesity because they lacked willpower or had a defect of character. For instance, they eat too fast, or they are overly responsive to the external cues of their environment that tell them to eat, while being unresponsive to the internal cues of satiation, as one popular theory of the early 1970s had it. “Fat Americans: They Don’t Know When They’re Hungry, They Don’t Know When They’re Full,” as a New York Times headline suggested in 1974. By that time, obesity, like anorexia, was categorized as an eating disorder, and the field of obesity therapy had become a subdiscipline of psychiatry and psychology. All these behavioral therapies, call them what you may, were in fact aimed at correcting failures of will. Every attempt to treat obesity by inducing the obese to eat less or exercise more is a behavioral treatment of obesity, and implies a behavioral-psychological cause of the condition.

Even if we accept that obese individuals are possessed of a defective character, then we’re still left in the dark. Why doesn’t the same defect—“the combination of weak will and a pleasure seeking outlook upon life,” said Louis Newburgh—cause obesity in everyone? “It exists in many non-obese individuals as well,” observed Hugo Rony; “in some of these it leads to chronic alcoholism, or drug addiction, others may become gamblers, playboys, prostitutes, petty criminals, etc. Evidently, such mental makeup, in itself, is not conducive to obesity. Those who do become obese apparently have something additional to and independent from this mental makeup: an intrinsic tendency to obesity.”