The specific ways exercise helps a body fight cancer cells

Source: ABC News, October 2011; Cancer Epidemiology, Biomarkers & Prevention, 2008; The Journal of the American Medical Association, 2005

Exercise has long been linked with reduced rates of breast and colon cancers, but studies are now exploring why. This ABC news report listed several recent discoveries.
First, fat cells in the body create more insulin and estrogen, both of which aid the growth of cancer cells. Exercise actually changes the composition of the body’s cells. It also helps reduce stress and inflammation, both of which have been linked to the growth of cancer cells. One study of 4,000 women with breast cancer found that those who reported the highest level of physical activity had half the risk of dying compared to breast cancer patients who did not exercise.
Another study found that women who walked 3-5 hours a week at an average pace saw the greatest benefits in terms of breast cancer. As one doctor explained, bodies are programmed to find and expel the dangerous cells that tend to circulate; exercise might be one of the ways the body does this.