A traditional discussion of obesity considers the number of pounds over what is considered average for one's age, height, and sex, and is based on the assumption that the average weight for a given group of people of the same age, height, and sex is the healthiest status for that group. There is a physiological and biochemical basis for obesity. Basically, fat has a number of constructive functions in the body: it supplies a reserve source of energy; serves as a medium for fat soluble vitamins; acts as an insulator from cold; and provides support and protection to body organs. However, excess adipose tissue places added strain on the circulatory, respiratory, and renal systems, and body composition is the only valid criterion for determining the state of obesity. The role of exercise and physical activity have been traditionally played down in weight control education, but physiologically these are vital because muscle cells are the most active metabolic cells in the body. Physical educators can play a major role in the furthering of obesity education by including in their curriculum a test of body composition and instilling in their students and future physical educators the idea that obesitv control is an individual responsibility. (DMT)