However, these mice develop insulin and leptin resistance, and are hence a valuable model to study genetically-induced obesity in a clinically relevant manner (Klebig et al., 1995; Miltenberger et al., 1997; Tschöp and Heiman, 2001; Rahmouni et al., 2002; Miyazaki et al., 2009). Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.