Forget the phony fountain of youth. If you want to live longer, go for a walk.

An analysis of studies of more than 650,000 people calculated how exercise affected life expectancy after age 40. About 10 years of follow-up showed that people who walked briskly for 15 minutes per day, five days a week, gained an average of 1.8 years of life. Those who exercised as often but for 90 minutes at a time added 4½ more years to their lives.

When weight was taken into account, the researchers learned that normal-weight people who walked 30 minutes per day, five days a week, gained 7.2 more years of life than sedentary obese people.

Source: PLOS Medicine, November 2012