A recent study from Stanford shows that 60 minutes per week of vigorous exercise wards off disabilities in seniors.
It makes sense; the more that we move about, increasing our circulation and our blood flow to important organs, we will be that much healthier. There doesn't seem to be a healthy outcome with a sedentary lifestyle, even though it seems like a popular lifestyle choice.
It would be good to see school programs focusing on life long habits of exercising rather than on the competitiveness of winning a game. American school phys-ed classes tend to focus on athletic students who can win games. This needs to change. Non-athletic students should feel safe in learning about exercise, rather than feeling shamed for their lack of prowess. Perhaps Yoga can become a school staple.
Exercise should become a life long habit for everyone. For details about the study: http://www.sciencedaily.com/releases/2008/06/080603185228.htm