Type 2 diabetes is considered by diabetes physicians as a complex and heterogeneous disease with a poorly understood aetiology, apart from the fact that there is a strong genetic propensity that becomes overt when exposed to a typical Western lifestyle. Our clinical targets are now moving from controlling the disease to preventing it. Do we need to await more research on the aetiology and pathophysiology before establishing a preventive strategy? No, the pathophysiology may be poorly understood, but there is now solid evidence that type 2 diabetes is a disease of fatness. New, controlled, clinical trials show that as little as 5% weight loss is sufficient to prevent most obese subjects with impaired glucose tolerance developing type 2 diabetes. Since type 2 diabetes is obesity dependent, and obesity is the main aetiogical cause of type 2 diabetes, we propose the term 'diabesity' should be adopted.