Obesity is an increasingly prevalent metabolic disorder affecting not only the US population but also that of the developing world. It is estimated from the third National Health and Nutrition Examination Survey (NHANES III)(1988-1991) that 33% of the US population is obese, compared with 25% in NHANES II (1976-1980). 1 Fatness is associated with a number of comorbidities, including several forms of heart disease. Although heredity explains 30% to 70% of cases of obesity, environmental contributions to the increasing prevalence of obesity must be sought since the gene pool has remained stable over the same interval. Diets high in fat (and calories) 2 and a reduced expenditure of energy in the form of physical activity 3 are the most likely explanations. However, in the United States, despite the reduction in consumption of fat from approximately 40% of calories in 1965 to 34% of calories in 1991, 4 a decrease in incidence of obesity has not occurred. This is likely attributable to both maintenance of fat intake with an increase in total caloric intake and reduced physical activity. Interestingly, in developing countries some comorbidities are seen at a lesser degree of excess weight, suggesting that relative weight may be as important as absolute adiposity.