Activation of MAP kinases not only by mitogenic insulin signaling but also by IGF1 signaling [18], together with overexpression of epithelial growth factor (EGF) or vascular endothelial growth factor (VEGF) in adipose tissue in obesity, may form a strong cell proliferation and growth stimulation scenario [17,18,19,21,24,25]. This evidence concerns the gene IGF1 and obesity due to melanocortin 4 receptor deficiency.