Thus, obesity is not simply a result of high energy intake and low energy expenditure; it is multifaceted, and inflammatory cytokines (increased TNF-α, IL-4, and IL-6; reduced IL-10), adipokines (e.g., adiponectin, leptin, resistin, and visfatin), and many other factors are involved in the pathogenesis of obesity [10,11]. Here, RETN is linked to obesity due to melanocortin 4 receptor deficiency.