MC4R and obesity due to melanocortin 4 receptor deficiency: In recent years, there has been increasing interest in the relationship between obesity-associated genes, such as the fat mass and obesity-associated (FTO), melanocortin-4 receptor (MC4R), transmembrane protein 18 (TMEM18), and brain-derived neurotrophic factor (BDNF) genes, and weight reduction or metabolic changes after behavioral interventions (13, 14).