Although exercising for health certainly isn’t a new concept, scientists recently uncovered one more reason to believe that couch potatoes may not live as long as their active counterparts. Researchers in London interviewed 2,401 Caucasian twins about their lifestyles, including the amount of exercise they get, smoking habits, and socioeconomic status. They then measured each person’s leukocyte telomeres (LTL), parts of the white blood cell that get shorter with age.

The study, published in the Archives of Internal Medicine, found that LTLs were longer in people who exercised regularly, suggesting that lack of exercise, in addition to smoking and other lifestyle choices, could lead to early aging. “Inactivity may diminish life expectancy not only by predisposing to aging-related diseases but also because it may influence the aging process itself,” the report says.