The prevalence of obesity in developed countries has been steadily increasing. Comprehensive lifestyle change programs for the treatment of obesity have garnered considerable empirical support, but most weight lost in lifestyle interventions is regained within several years. The outcome of obesity prevention programs has also been disappointing. One reason for this state of affairs may be that most weight control programs are based on an assumption of equipotentiality of their intervention components. That is, obesity prevention and treatment programs consist of a multitude of behavioral, cognitive, nutritional, physical activity, and interpersonal techniques, all of which are assumed to be of roughly equal importance in weight control. However, there is considerable evidence that our evolutionary heritage has made most humans highly sensitive to the availability and nature of food in the environment. It therefore may be unrealistic to expect that enhancing self-regulatory skills will be sufficient to overcome the combined influence of our appetitive predispositions and the obesigenic environment. However, there is growing evidence that weight control interventions that focus on the availability, structure, composition, and portion size of foods in the diet improve long-term weight control. Concerted efforts to change the availability and nature of foods at both the individual and population level may hold considerable promise for the treatment and prevention of obesity.