A recent study measuring body height and weight in a random sample of several thousand men and women in the United States found the prevalence of overweight, 28% in the 1970s, had risen to 33% [1], Not only are more Americans overweight but also the average weight has increased an astonishing 8 lb in the last 10 years. This average gain in weight translates to a 1–2 unit increase in body mass index (BMI; kg/m2). BMI, in turn, is a simple criterion established by National Institutes of Health Consensus Conference to guide physicians regarding the relative importance of intervention [2] (Table 1)Whereas the medical complications of obesity-glucose intolerance, hypertension, dyslipi-demia, coronary artery disease, gallstones, arthritis, etc-are well established [3], an effective treatment program for obesity-weight loss-is not well established [4]. This article reviews how effective commonly used treatments of obesity are at producing weight loss.