Obesity, in particular visceral obesity, is associated with impaired insulin action on target tissues (insulin resistance or metabolic syndrome) that, in turn, is related to an increased risk for cardiovascular mortality and morbidity. Pathophysiological mechanism remains unclear. Interventions in patients with impaired glucose tolerance/impaired fasting glucose have consistently demonstrated that by increasing physical activity and reducing calorie intake the risk to convert to frank type 2 diabetes is decreased, even more efficiently than by early medical therapy with metformin.