RETN and obesity due to melanocortin 4 receptor deficiency: Conversely, caloric restriction and the treatment with orlistat, an anti-obesity drug, determined—both in animal models and in vitro—a reduction in melanoma progression, likely related to the normalization of resistin and leptin serum levels secondary to adiposity reduction, with a lower synthesis of FASN, Cav-1, and activated protein kinase B (Akt) levels [23].