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And if their parents' generation inaugurated the science of good nutrition — the five food groups and all that — the boomers' adult years have, fittingly enough, produced a major new body of evidence on the benefits of "getting physical."

In fact, this evidence suggests that exercising regularly during middle age and beyond is an enormously effective way to promote just the sort of old age boomers dream about: independent, robust and free of chronic disease or disability. "If you had to pick one thing, one single thing that came closest to the fountain of youth," says James Fries, M.D., a pioneer researcher on healthy aging at Stanford University, "then it would have to be exercise."

Exercise maintains healthy blood vessels for good circulation in the body and brain. It also helps people manage their weight and cope with stress. And exercise stems age-related losses in bone density and muscle mass while it keeps the heart and lungs strong.

The bottom line, reflected in dozens of studies, is that people who exercise, on average, live longer than those who don't, with a reduced chance of heart disease, high blood pressure, stroke, type 2 diabetes, colon and breast cancers, depression, falls and even mental decline.