What you can gain by exercising longer and harder

New evidence indicates that more frequent and more vigorous activity can turn back the biological clock.

Fifteen minutes of vigorous exercise or 30 minutes of moderate activity several times a week can reduce your risk of cardiovascular disease, obesity, diabetes, cancer, depression, and dementia. But according to recent studies, exercising even more vigorously for longer periods may have additional benefits by taking years off your biological age. It does so by increasing aerobic capacity—the amount of oxygen you can take in and distribute to your tissues in a minute. "Some studies have indicated that people in their 80s who exercised at high intensity for 20 to 45 minutes a day have an aerobic capacity of people 30 years younger," says Dr. J. Andrew Taylor, director of the cardiovascular research laboratory at Harvard-affiliated Spaulding Rehabilitation Network.