Obesity is nowadays considered as a chronic low-grade inflammatory status which is closely related to the release, by white adipose tissue, of a plethora of factors, most of them of proinflammatory nature, including classical cytokines such as IL-6, IL-1 and TNF-α, as well as adipokines, such as leptin, adiponectin, resistin, visfatin, and other recently identified factors such as chemerin, lipocalin, or serum Amiloyd 3 (SAA3) [6–8]. Here, RETN is linked to obesity due to melanocortin 4 receptor deficiency.