Regular physical activity, fitness, and exercise are critically important for all people's health and wellbeing. It can reduce morbidity and mortality from many chronic diseases. Despite its well-known benefits, most U.S. adults, and many children, are not active enough to achieve these health benefits. Physical inactivity and related health problems have substantial economic consequences for the health care system. Increasing prevalence of chronic medical conditions and diseases related to physical inactivity relate to costs for preventive, diagnostic, and treatment services and costs associated with the value of lost wages by people unable to work due to illness and disability. Participation in regular physical activity is critical to sustaining good health. At least 30 minutes of moderate activity on at least 5 days per week or 20 minutes of vigorous physical activity at least 3 days per week is important. Regular physical activity can reduce morbidity and mortality from mental health disorders. It is also key to maintaining energy balance and healthy weight. Due to lifestyle and dietary changes, overweight and obesity have reached epidemic proportions. Morbidity and mortality associated with overweight and obesity has increased. Because physical inactivity is a risk factor for many diseases and conditions, making it an integral part of daily life is crucial. (Contains 34 references.) (SM)