MC4R and obesity due to melanocortin 4 receptor deficiency: Consequently, in our study, we decided to analyze five of the most promising polymorphic sites localized within obesity-related genes: fat mass and obesity-associated (FTO), fatty acid-binding protein 2 (FABP2), leptin (LEP), leptin receptor (LEPR), and melanocortin-4 receptor (MC4R), which are characterized in Table 1 [9,16,17,18,19,20,21,22].