As such, leptin is considered as a prominent catabolic hormone, since disruption of the gene coding for leptin (ob/ob mice) and/or its receptor (db/db mice) induces massive obesity, resulting from hyperphagia and reduced BAT thermogenesis (Thenen and Mayer, 1976; Leiter et al., 1983; Malik and Young, 1996; Mizuno et al., 1998; Goncalves et al., 2009). The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.