How can physical activity reduce breast cancer risk?
Physically active women have up to a 40 percent reduced risk of developing breast cancer (4, 16). Most evidence suggests that physical activity reduces breast cancer risk in both premenopausal and postmenopausal women (14-20). Although a lifetime of regular, vigorous activity is thought to be of greatest benefit, women who occasionally engage in physical activity also experience a reduced risk compared to inactive women (17, 20). A number of studies also suggest that the effect of physical activity may be different across levels of Body Mass Index (BMI), with the greatest benefit seen in women in the normal weight range (generally a BMI under 25 kg/m 2 ). For example, a recent major report from the Women’s Health Initiative found that among postmenopausal women, walking 30 minutes per day was associated with a 20 percent reduction in breast cancer risk. The health benefits of physical activity were greatest among women who were of normal weight; they experienced a 37 percent decrease i
