The increasing prevalence of obesity is accompanied by an increasing prevalence of type 2 diabetes. Obesity not only increases the risk of developing type 2 diabetes but also compounds its health risks and complicates its management. The health benefits of weight loss and the efficacy of current weight loss strategies in obese persons with type 2 diabetes are evaluated. In addition, the article reviews the results of lifestyle intervention trials designed to reduce conversion to type 2 diabetes in at-risk individuals.