Physical activity and breast cancer risk

To provide the current evidence linking physical activity to breast cancer risk, the objectives of this review were twofold: (1) to review the epidemiological literature examining the relationship between physical activity and breast cancer risk; and (2) to summarize the mechanisms through which physical activity can influence risk. A review of the literature was conducted to identify studies that addressed these two objectives. Of the 76 studies reviewed, 40 (53%) reported a protective effect of physical activity on breast cancer risk. The protective effects of physical activity on breast cancer risk are likely to be through changes in sex hormone levels, immune function, adiposity, and insulin-related hormones. To achieve the greatest reduction in risk of breast cancer, regular participation in physical activity should begin in childhood and persist throughout the lifespan.