Among all metabolic disorders caused by obesity, insulin resistance (IR) is one of the most important as it is associated with a chronic state of subclinical inflammation, characterized by increased serum concentrations of C-reactive protein (CRP) [3], interleukin (IL)-6, IL-8, monocyte chemotactic protein (MCP)-1 [4], tumor necrosis factor (TNFa) [5], amyloid A, resistin, leptin, and adiponectin [6, 7]. Here, RETN is linked to obesity due to melanocortin 4 receptor deficiency.