Exercise to stay young

A newly released British study finds that people who exercise at least three hours a week are up to nine years younger 'biologically' than people who are sedentary. The study of 2,401 twins found that those who exercised vigorously for at least three hours each week were biologically younger than those who did uner 15 minutes. People who did moderate exercise for 1 1/2 hours each week got a four-year advantage. Researchers aren't sure what causes the effect, but it's believed physical activity somehow defends against a natural process called oxidative stress, which damages and kills cells. The study also backed up previous research that has found a sedentary lifestyle raises the risk of a range of problems from heart disease to cancer.