Mean Native American ancestry of the chromosome 18 segment containing the MC4R Ile269Asn mutation was estimated in 206 patients with obesity, and was 58% in wildtype homozygous individuals, 79% in heterozygous patients and 100% in the Asn269Asn homozygous patient (Supplementary Table S2). This evidence concerns the gene MC4R and obesity due to melanocortin 4 receptor deficiency.