Review Physical Activity and Postmenopausal Breast Cancer: Proposed Biologic Mechanisms and Areas for Future Research

Convincing evidence now supports a probable pre-ventive role for physical activity in postmenopausal breast cancer. The mechanisms by which long-term phy-sical activity affect risk, however, remain unclear. The aims of this review were to propose a biological model whereby long-term physical activity lowers postmeno-pausal breast cancer risk and to highlight gaps in the epidemiologic literature. To address the second aim, we summarized epidemiologic literature on 10 proposed biomarkers, namely, body mass index (BMI), estrogens, androgens, sex hormone binding globulin, leptin, adi-ponectin, markers of insulin resistance, tumor necrosis factor-A, interleukin-6, and C-reactive protein, in rela-tion to postmenopausal breast cancer risk and physica