This manuscript presents a brief summary of the substantial data supporting an inverse relationship between the amount of habitual physical activity performed and a variety of negative health outcomes throughout the lifespan. It points out that despite these data a large segment of the US population remain insufficiently active resulting in a high population attributable risk for chronic disease due to inactivity. The accumulated data support the need for more comprehensive health promoting physical activity policies and programs, especially for the economically and socially disadvantaged and medically underserved.