I asked this as well, literally Googling up "Does exercise prevent cancer", and what I found isn't all that great: https://www.cancer.gov/about-cancer/causes-p

I asked this as well, literally Googling up "Does exercise prevent cancer", and what I found isn't all that great: https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/physical-activity-fact-sheet https://www.cancer.gov/about-cancer/causes-prevention/risk/o... >Nearly all of the evidence linking physical activity to cancer risk comes from observational studies, in which individuals report on their physical activity and are followed for years for diagnoses of cancer. Data from observational studies can give researchers clues about the relationship between physical activity and cancer risk, but such studies cannot definitively establish that being physically inactive causes cancer (or that being physically active protects against cancer). That is because people who are not physically active may differ from active people in ways other than their level of physical activity. These other differences, rather than the differences in physical activity, could explain their different cancer risk. For example, if someone does not feel well, they may not exercise much, and sometimes people do not feel well because they have undiagnosed cancer. I would really like to see some proper studies done. Unfortunately, seeing friends and otherwise healthy, physically active people passing away from cancer at a relatively young age does not inspire hope at the moment.