There is still much debate and uncertainty about both phenotypic association and protein functionality of FTO. Human FTO protein expression studies fail to replicate FTO's association with obesity observed in mouse models (Klöting et al., 2008; Wåhlén et al., 2008; Grunnet et al., 2009). The gene discussed is FTO; the disease is obesity due to melanocortin 4 receptor deficiency.