There has been increasing interest in the effects of chronic dieting and of repeated cycles of weight loss and regain in athletes. The purpose of this investigation was to examine the eating and weight loss practices, nutrition, and psychological factors in 45 male body builders competing in a drug-free competition. Subjects completed a questionnaire on the morning of a body building competition to assess the weight loss and dietary history, psychological distress, reports of binge eating, and vitamin and mineral supplement usage. The subjects reported high levels of dieting, weight loss, and weight regain. The mean weight loss reported in the competitive season was 6.8 kg; the mean weight gain reported was 6.2 kg. Eighty-five percent reported gaining weight while 46% reported episodes of binge eating after competitions. Most (81.5%) reported being preoccupied with food sometimes, often, or always. Between 30 and 50% reported psychological distress when preparing for competition (anxiety, short temper, anger). A similar number (30-50%) reported using amino acid, protein, and vitamin supplements. It appears that severe dieting practices are common in the sport of competitive body building. The potential physiological, psychological, and health implications of these practices, combined with the growing popularity of body building, are of sufficient importance to warrant further attention by investigators and the body building community.