We reviewed the psychosocial consequences of weight reduction and concluded that weight loss is usually associated with improvements in mood in significantly obese individuals (> or = 20% overweight) who are treated by diet and lifestyle modification. Less is known about the psychologic effects of weight loss in mildly overweight individuals who reduce their weight on their own but the limited data suggest similarly positive effects. We recommend that significantly obese individuals seek a 10% reduction in body weight, a loss that is likely to be associated with improvements in psychologic as well as physical health. A loss of this magnitude is typically produced by 16-20 wk of treatment by diet and behavior modification. Persons who ae mildly overweight (particularly those with health complications) are encouraged to reduce their weight by increasing their physical activity. Exercise is associated with modest but long-term weight losses and with improvements in mood and physical health. The recommendation that overweight Americans seek a healthier weight should be combined with efforts to promote healthier attitudes toward weight and shape in normal-weight women and girls.