Mice lacking the β-adrenergic receptors develop massive obesity (Bachman et al., 2002), whereas β3-adrenergic agonists elicit potent effects on energy homeostasis by suppressing food intake, and promoting body fat loss, lipid oxidation, oxygen consumption and mitochondrial biogenesis, as well as improving insulin sensitivity and glucose tolerance (Arch and Wilson, 1996; Granneman et al., 2005; Lowell and Spiegelman, 2000; White et al., 2004). The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.