In adults, loss of 10% of body weight improves many obesity-associated comorbid conditions, such as hypertension, dyslipidemia, and glucose intolerance (6). Furthermore, the Diabetes Prevention Program (11) demonstrated that a lifestyle intervention with a goal to achieve modest weight loss and increase physical activity in glucose-intolerant adults statistically significantly reduced the incidence of type 2 diabetes mellitus. Physical activity alone also improves glucose intolerance, as well as blood pressure and dyslipidemia (12). Because we know considerably less about the effect of weight loss or physical activity on obesity-associated comorbid conditions in children and adolescents, Berkowitz and colleagues' study provides welcome new information. Those who lost weight in the sibutramine group of the study had improved levels of triglycerides, high-density lipoprotein cholesterol, total cholesterol, insulin, and insulin sensitivity. Physical activity was a component of the behavioral intervention, but because the authors did not analyze the effect of behavioral intervention separately from that of sibutramine, it is difficult to know what proportion of the improvements in comorbid conditions was attributable to the weight loss and what proportion was attributable to increased physical activity.