We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
I fully support exercise for a healthier life. However I am wary of so-called scientific studies. Perhaps the intent is good, the well meaning doctors want us to do what is healthy so let's tell a little white lie and where is the harm.
Statistics is a funny thing. After all half of America's students are below average after years of spending more on education. So if we just double the spending maybe we can change that. But of course statistically half of everyone will be below average all the time no matter what. But with the language of statistics it sounds convincing.
So what do the studies really say about the value of exercise to "prevent" cancer. Well the percentage that the claim is based on is very thin. These thin differences can be the result of a small or poorly defined study group or issues that have little or nothing to do with the study or unknown factors.
One last point. Very few actual controlled "studies" are done anymore. Typically what these "studies" really are is simply a data dredge. That is someone, typically a graduate student, with an agenda, their own or their mentor's, searches through a number of data sources for any correlation that supports their hypothesis while ignoring or disregarding anything that does not. Then finding even a small but still statistically insignificant correlation, is published as "proof" of the hypothesis. And the unsuspecting public laps it up.
SO exercise for the right reasons. It is generally good for your body especially if you avoid overdoing it and injuring yourself. It It will make you fell good about yourself and increase your physical abilities. It can be part of a weight loss program. Exercise is a good thing but unlikely to prevent cancer.