Recent changes in lifestyle, including physical inactivity and unhealthy diets, are likely to have played an important role in the global epidemic of obesity, type 2 diabetes, and metabolic syndrome. Implementation of a healthier lifestyle, with an increase in physical activity and a reduction of body weight, based on the regulation of calories and fat intake, are the basis for the prevention and treatment of both type 2 diabetes and metabolic syndrome. Intervention studies based on changes in lifestyle in individuals at risk found that diabetes incidence was reduced by 42% to 63%. Similarly, intensive lifestyle changes in patients with the metabolic syndrome have been shown to reduce the prevalence of the syndrome by 20% to 48%. Reduction of body weight, improvement of the quality of diet, and promotion of physical activity are the main approaches to prevent and treat patients with type 2 diabetes or metabolic syndrome.