Physical activity reduces the risk of postmenopausal breast cancer, but the biologic mechanisms underlying this association are not well understood. Insulin
insulin-like growth factor 1 (IGF1 and its binding proteins; Yu & Rohan
2000, Lann & LeRoith 2008) leptin (Catalano et al.2003, Geisler et al. 2007, Cirillo et al. 2008), and adiponectin are metabolic factors hypothesized to mediate the association between physical activity and postmenopausal breast cancer risk .