Exercise helps maintain telomeres
In this 2008 study of twins, British researchers looked at 52 pairs of identical and 15 pairs of fraternal twins and concluded that exercise, even after controlling for confounding variables of age, BMI, smoking, year of sampling, and socioeconomic status, was associated with telomere length preservation. The effect was 6 years of length for 100 minutes a week and 9 years of advantage for 3 hrs or more.