Candidates that might modify the effect of water intake on adiposity include single-nucleotide polymorphisms (SNPs) in obesity-associated genes including, representatively SNPs in the fat mass and obesity-associated gene (FTO) (rs9939609, T>A) [6–8], near the melanocortin 4 receptor gene (MC4R) (rs17782313, T>C) [9–11], in brain-derived neurotrophic factor gene (BDNF) (rs6265, C>T) [12, 13]. The gene discussed is MC4R; the disease is obesity due to melanocortin 4 receptor deficiency.