Rising obesity rates are rapidly becoming a growing health concern in the developing world. The fat mass and obesity associated gene (FTO) is the first gene discovered to contribute to common forms of human obesity. FTO is a member of the non-heme dioxygenase superfamily, encoding a 2-oxoglutarate-dependent nucleic acid demethylase whose mRNA is widely expressed, especially in neurons of feeding-related nuclei of the brain. FTO mRNA in the arcuate nucleus in mice is up-regulated by feeding and down-regulated during fasting, although the opposite pattern has been observed in rats. At least four isoforms of FTO are known to exist.