FTO and obesity due to melanocortin 4 receptor deficiency: The FTO gene has not been previously implicated in obesity, but it maps to a region where linkage to BMI has been reported in two previous genome-wide linkage scans (LOD = 3.2 in the Framingham Heart Study [32] and LOD = 2.2 in the families with white ancestry from the Family Blood Pressure Program [33]).