Obesity is a major public health problem and is a result of the interaction between environment and genetic factors. There are now at least 20 single genes that have been discovered to be associated with an autosomal form of human obesity. Genome-wide association studies are beginning to identify the common genetic variations that underpin difference in adiposity across the normal population. FTO has been shown to be a dioxygenase with an ability to demethylate 3-methylthymine in DNA in vitro, and is the first common obesity gene. Obesity is not only a metabolic disease but also more of a neurobehavioural disorder.