“Inactivity is associated with increased risk for a number of cancers, including colon and breast cancer,” McCleary says. “Exercise has been linked with a decreased risk of developing cancer, death from cancer, and recurrence of certain cancers.” The suggested mechanisms at play include exercise’s beneficial effects on the immune and surveillance systems that detect and kill cancer cells, improved cardio-respiratory status, improved hormonal profiles, weight maintenance, and other beneficial metabolic effects, he says.
Exercise has long been correlated with a longer life, but it’s only recently started to become clear why this might be. Studies, like a new one in the journal Preventive Medicine which found that exercise is linked to longer caps at the ends of chromosomes, have helped flesh this out a bit more. These caps, called telomeres, naturally shorten as we age, with each cell division. People who live a long time have telomeres that are in better shape than those who don’t—but there’s a lot we can do to affect the rate at which they shorten over the years. The team behind the new study looked at data from CDC's National Health and Nutrition Examination Survey, and found that for people who exercised regularly, their telomeres were 140 base pairs longer on average than sedentary people's. Which correlates to being years “younger” than their sedentary peers.