TMEM18 and obesity disorder: For example, the transmembrane protein 18 (TMEM18) gene and melanocortin-4 receptor (MC4R) have a function in regulating food intake; fatty acid-binding protein 2 (FABP2) is involved in lipid metabolism; peroxisome proliferator-activated receptor-gamma (PPARG) and the fat mass- and obesity-associated (FTO) locus have a role in adipocyte differentiation.