Everyone knows exercise is good for controlling pain, weight, sleeping and just plain feeling better. And studies show it can help prevent diseases associated with aging such as heart disease, cancer, osteoporosis and high blood pressure. But can exercise actually slow the aging process?

Researchers at King’s College London, in the United Kingdom believe it can. Their study compared participant's telomeres – sequences of DNA found at the end of a chromosome that protect chromosomes from damage. Telomeres get shorter and can’t play their role of protector as well as people continue to age and cells die off. Shorter telomeres mean older, more tired cells.

However, the telomeres of participants who exercised more in their leisure time were longer than the telomeres of people who didn’t get as much physical activity. That led researchers to conclude that people who exercise regularly are biologically younger than those who are sedentary.

A study in Germany at Saarland University Clinic in Homburg backs up these results even more dramatically. Researchers there found that telomeres in young people who were both highly active and highly inactive were about the same size. And while telomeres in sedentary middle-aged subjects were some 40 percent shorter than those of their sedentary younger counterparts, the telomeres of active middle aged subjects were only about 10 percent smaller than those of equally active young participants.

So far, researchers aren’t sure what the link is between exercise and telomere length – it could be that sedentary lifestyles increase the risk for inflammation and cell damage, which are associated with aging. Or exercise may lower stress, which other studies have shown can affect telomere length.

How much exercise is enough to get the benefit? The most active people in the Kings College study exercised an average of 199 minutes a week – equivalent to a little less than 30 minutes a day. That’s in line with recommendations from the Centers for Disease Control and Prevention, which urges 30 minutes or more of moderate-intensity exercise, five or more days a week.