More than half of adult Americans are overweight or obese, and public health recommendations call for weight loss in those who are overweight with associated medical conditions or who are obese. However, some controversy exists in the lay press and in the medical literature about the health risks of obesity. We review briefly the large body of evidence indicating that higher levels of body weight and body fat are associated with an increased risk for the development of numerous adverse health consequences. Efforts to prevent further weight gain in adults at risk for overweight and obesity are essential. For those whose present or future health is at risk because of their obesity and who are motivated to make lifestyle changes, a recommendation for weight loss is appropriate.