Type 2 diabetes and metabolic syndrome are two of the fastest growing public health problems in both developed and developing countries. Cardiovascular disease is the most prevalent complication of type 2 diabetes and the metabolic syndrome. Overweight, obesity, or weight gain has been shown to be an important risk factor for the development of type 2 diabetes and an important component of the metabolic syndrome. Physical inactivity is another important risk factor for the development of type 2 diabetes. Data from prospective studies have shown that at least 30 min/day of moderate to vigorous physical activity can prevent type 2 diabetes. Moderate or high levels of physical fitness are effective in preventing type 2 diabetes. Results from clinical trials have indicated that lifestyle changes, including dietary modification and increase in physical activity, can prevent type 2 diabetes. Analyses from prospective studies have confirmed that healthy diets are effective and safe ways to prevent type 2 diabetes and the metabolic syndrome. Public health messages, health care professionals, and the health care system should aggressively promote physical activity and responsible nutritional habits during occupation, leisure time, and daily life and prevent overweight and obesity.