Can you please tell me why doing anything seems to reduce or increase risk of cancer?

Media junk: Studies looking at correlations are suspect because of confounding variables (most runners don't smoke), recall bias ("i must have been around power lines for junior to get cancer") and lying (burger-eaters might lie about fitness habits). Junk (including epa) work on animals uses preposterous amounts of chemicals making anything cause cancer. All this makes us real-science people angry too.