Just by enjoying moderate physical activity on a regular basis — which can be whatever activities bring you the greatest joy, from walking through a park to running a marathon — you are preventing obesity, reducing hormone levels, and strengthening your immune system. All of these very achievable benefits have been linked to lowering the risk of cancer. In fact, controlling your weight and diet, combined with engaging in physical activity, improves your cardiovascular system, your respiratory system, and your health in general.

Physical activity has also been positively associated with reduced risk of a number of specific cancers:

• Protection against colon cancer — Physical activity can dramatically reduce the risk of developing colon cancer, positively impacting immune-system factors which may diminish colon cancer risk and limiting the time the colon has exposure to carcinogens.
• Protection against breast cancer — Physical activity lowers the risk of women developing breast cancer as well by lowering hormone levels and insulin levels, strengthening the immune system, and enabling weight maintenance that can help to prevent excess body fat.
• Protection against uterine cancer — Physical activity also reduces a woman’s risk of developing uterine cancer, probably by stabilizing life-cycle changes in body mass and in the levels and metabolism of estrogen and other sex hormones.
• Protection against lung cancer — There is also a correlation between physical activity and a diminished risk of developing lung cancer, which may be attributable to the seemingly logical notion that those who exercise would be less likely to smoke tobacco.