Don't retire. "Evidence shows that in societies where people stop working abruptly, the incidence of obesity and chronic disease skyrockets after retirement," says Luigi Ferrucci, director of the Baltimore Longitudinal Study of Aging. The Chianti region of Italy, which has a high percentage of centenarians, has a different take on leisure time. "After people retire from their jobs, they spend most of the day working on their little farm, cultivating grapes or vegetables," he says. "They're never really inactive." Farming isn't for you? Volunteer as a docent at your local art museum or join the Experience Corps, a program offered in 19 cities that places senior volunteers in urban public elementary schools for about 15 hours a week.