A study from Calgary shows that a regular exercise program can reduce a woman's chances of suffering breast cancer. Exercising after the menopause was even more effective than exercising in early life in preventing breast cancer.

Nobody really knows how exercise may prevent breast cancer. Since estrogen stimulates the breast to grow, having too much estrogen increases a woman's chances of developing breast cancer. When a woman goes into the menopause, her ovaries stop making estrogen and her main source of estrogen is her fat cells, which convert male hormones produced by her ovaries and adrenal glands into estrogen. So obese postmenopausal women have the highest estrogen levels and therefore are at increased risk for developing breast cancer. The vast majority of women gain weight after the menopause. The best way to prevent this weight gain is to continue to exercise vigorously as you grow older.

Influence of physical activity in different age and life periods on the risk of breast cancer. Epidemiology, 2001, Vol 12, Iss 6, pp 604-612. CM Friedenreich, KS Courneya, HE Bryant.

Reported 8/11/01; checked 9/3/05

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