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Breast cancer is the second most common cancer in women.  There are many risk factors for developing breast cancer, including age, race, gender, family history, alcohol use, smoking, diet, weight and exercise. 

Women who have been pregnant or breastfed have a lower risk of breast cancer because of the lowered estrogen levels during these times. 

Exercise has been shown to reduce estrogen levels too.  After twelve months of regular exercise,  blood estrogen levels drop an average of about 13% in women who lose at least 1Kg.  Vigorous exercise reduces the risk of breast cancer about 30%.