Article Summary Obesity and diabetes. Cornier M-A. Curr Opin Endocrinol Diabetes.. 2005;12:260-266. Objective: To review recent data on obesity and diabetes with an emphasis on the effects of weight loss and the effectiveness of weight loss therapies in patients with type 2 diabetes. Observations: The prevalence rates of diabetes (6.3%) and of obesity (~67%) in the United States have dramatically increased and continue to rise at a disturbing rate. Data from the Health Professionals Follow-up Study (2004) suggest that for every kilogram of weight gained, the risk for diabetes increases by 7.3%. Obesity significantly increases a person’s risk for developing type 2 diabetes; it also exerts negative effects on disease progression and treatment outcomes for patients with diabetes and associated comorbidities. Population-based studies have shown, on the other hand, that weight loss is associated with a reduced risk for developing diabetes, decreased mortality, improved glycemic control and insulin sensitivity, and favorable effects on cardiac risk factors, such as lipids and blood pressure. A low-fat diet that results in moderate weight loss, combined with an increase in level of activity, has been noted to have profound effects in the treatment and prevention of diabetes. Conclusions: Obesity is a significant risk factor for the development of type 2 diabetes. It promotes disease progression and impedes the effectiveness of therapies undertaken to treat patients with, or prevent the onset of, diabetes. Dietary intervention undertaken to reduce risk factors is the cornerstone of weight loss treatment. However, controversy continues over which type of diet is optimal for managing obesity and diabetes. Further study is needed. In addition, pharmacotherapy and bariatric surgery offer promise as tools to promote weight loss while reducing other cardiac risk factors, such as hyperlipidemia and hypertension.