Fat mass and obesity related protein (FTO) gene is the most robust gene for common obesity characterized to date. FTO gene expression has been found to be significantly upregulated in the hypothalamus of rats after food deprivation and strongly negatively correlated with the expression of orexin peptide which is involved in the stimulation of food intake. Deletion analysis of FTO gene in mice showed that FTO is functionally involved in the control of both energy intake and energy expenditure.