IGF1 and Insulin resistance: Various mechanisms by which diet and lifestyle may promote BC have been reviewed previously (Kaaks, 1996; Vainio and Bianchini, 2002; Lorincz and Sukumar, 2006), suggesting that a sedentary lifestyle, overweight, and a fat-rich diet are associated with insulin resistance and increased androgenic activity, whereas physical activity improves insulin sensitivity and decreases testosterone and insulin-like growth factor 1 (IGF-1) levels.