Results from ecological and migration studies indicate that a western lifestyle is associated with a higher prevalence of type 2 diabetes. In recent years, there has been a rapid accumulation of data on lifestyle and risk for type 2 diabetes from studies on an individual level. This article gives an overview of the evidence for the effect of different lifestyle factors on risk for type 2 diabetes and discusses various methodological approaches. Randomized intervention studies have shown that changes in diet and physical activity can protect against type 2 diabetes. Diet and physical activity can affect the development of type 2 diabetes through changes of body fatness, but also through other pathways. Findings from cohort studies and trials with intermediary endpoints have indicated that higher consumption of whole grain products and exchanging unsaturated fat for saturated fat may lower risk for type 2 diabetes. In addition, several new promising hypotheses about diet and the development of type 2 diabetes are currently being investigated. Light to moderate alcohol consumption may also reduce risk for type 2 diabetes, whereas high alcohol consumption and cigarette smoking may increase risk for type 2 diabetes. Prevention of weight gain by balancing energy intake and expenditure is of paramount importance to limit current increases in the prevalence of type 2 diabetes. In addition, other effects of lifestyle may play an important role in reducing risk for type 2 diabetes.