IL22 and obesity due to melanocortin 4 receptor deficiency: Although the work of some authors might suggest that this constitutes a protective effect toward the development of obesity (Figure 1D) (78, 79), Park et al. argue that low, physiologic levels IL-22 are unlikely to contribute to the pathogenesis of HFD-induced obesity and its metabolic sequelae, which is supported by other studies (68, 80).