Obesity Many Americans are at increased health risk because they are obese. The U.S. Surgeon General, in a 1988 report on nutrition and health, estimated that one-fourth of adult Americans are overweight. Obesity is a known risk factor for chronic diseases including heart disease, diabetes, high blood pressure, stroke, and some forms of cancer. Everyone needs a certain amount of body fat for stored energy, heat insulation, shock absorption, and other functions. As a rule, women have more fat than men. Doctors generally agree that men with more than 25 percent body fat and women with more than 30 percent body fat are obese. Precisely measuring a person's body fat, howeve