In animals, dwarf, long-lived mice lacking the growth hormone receptor (GHR-/-) have reduced levels of IGF-1, are insulin sensitive despite obesity, and have decreased risk for cancer and diabetes (Zhou et al., 1997; Shevah & Laron, 2007; Ikeno et al., 2009). This evidence concerns the gene GHR and obesity due to melanocortin 4 receptor deficiency.