Ob/Ob, and Db/Db obese rodent mutants, and diet-induced obesity mammals have reduced STAT-3 signaling in the arcuate nucleus which is generally attributed to either an absence of the hormone, an inability to respond to the hormone, or central leptin resistance (Ghilardi et al., 1996; Münzberg, Flier & Bjørbæk, 2004; Vaisse et al., 1996). This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.