Research suggests that individuals who were never heavy, were once heavy but lost weight, or who are currently obese can be differentiated by physical self concept, number of hours spent in various activities, and the hierarchial reinforcement value of different behaviors. Subjects (N=99) completed the Tennessee Self-Concept Test, the Self-Control Schedule, the Paired Comparison Reinforcement Scale, the Health Locus of Control, and the Activities Questionnaire. Results indicated that obese individuals had a lower physical self-concept than persons in the other two groups. No differences in self-concept were found between the never-heavy and the once-heavy groups, belying the notion that overweight people continue to perceive themselves as obese after they become thin. The never-heavy individuals spent more time in vigorous activity, less time doing job-related work, and more time with friends than individuals in the other groups. The obese group found eating or engaging in passive activity more reinforcing than other groups. Findings indicate that persons who find food highly reinforcing and choose passive activities over physical activities are more likely to be overweight, have little self-control, and have low physical and total self-concepts. (Author/JAC)