FTO and obesity due to melanocortin 4 receptor deficiency: In obedience to a systematic review (53), several genes are strongly associated with MetS in schizophrenia patients such as the fat mass and obesity associated gene (FTO), leptin and leptin receptor genes (LEP, LEPR), methylenetetrahydrofolate reductase (MTHFR) gene, and the serotonin receptor 2C gene (HTR2C).