INS and obesity due to melanocortin 4 receptor deficiency: Insulin has long been regarded as a possible mediator of the effects of obesity and physical inactivity on colorectal cancer risk (McKeown-Eyssen, 1994; Giovannucci, 1995; Strickler et al, 2001), since, in addition to its role in metabolism, insulin has mitogenic and anti-apoptotic activity (Koenuma et al, 1989; Bjork et al, 1993; Wu et al, 1995; Bruce and Corpet, 1996).