Future studies are needed to determine how they contribute to substrate recognition by FTO. Previous study also showed that FTO was widely expressed in fetal and adult tissues, with the highest expression found in the brain tissue, which is a key controller of energy balance; thus, variation in expression may result in carriers of the risk allele (A) and develop obesity through excessive ingestion rather than altered energy consumption. Here, FTO is linked to obesity due to melanocortin 4 receptor deficiency.