Increased fitness in middle life can have a significant reduction in cases of cancer for men, a study has found Increased fitness in middle life can see a significant reduction in cases of cancer for men, a study has found Keeping fit reduced the chances of those who developed lung, bowel or prostate cancer dying from their disease by almost a third, the research showed. Mid-life fitness also lowered the risk of being diagnosed with lung and bowel cancer, but apparently not prostate cancer.