This question is built into the logic of the overeating/sedentary-behavior hypothesis. Why do people overeat, or why are they so sedentary, if the inevitable result is obesity? And because both overeating and deficient physical activity are, after all, behavioral conditions, not physiological ones, the only answer allowed by the hypothesis is a judgment on the behavior of the obese. To say that the obese eat more than they should, as Johnson phrased it, or are less active than they should be—thus, inducing their positive caloric balance—implies only two possibilities. Either it’s beyond their control, in which case there is another, more profound cause of their condition—perhaps a metabolic or hormonal disorder for which we should still be searching—or it is within their control, and so we are led to the judgment that the obese are weaker of will than the lean. It may be true, as von Noorden noted, that their appetite is unable to regulate their energy consumption, but why, then, do they not consciously adjust? The 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.