The Real Fountain of Youth: Exercise

"Exercise seems to be one of the key factors that distinguish people who have a healthy old age from those who don't," says Suzanne Leveille, a professor of nursing at the University of Massachusetts Boston who is conducting research on disability in older people. "Being sedentary is a known risk factor for just about every poor health outcome, from being hospitalized to ending up in a nursing home, and even to mortality."

In terms of longevity, regular exercise seems to have an impact that few other health measures can match.

Compared with sedentary men and women, people who did an hour and a half of moderate-to-vigorous physical activity weekly — less than 15 minutes a day — were 20 percent less likely to die during a follow-up period of more than a decade, according to a 2008 report by a federal guidelines committee. And when these exercisers spent more time moving — an hour a day — they cut their risk of dying by a whopping 40 percent.