FTO and obesity due to melanocortin 4 receptor deficiency: In the meta-analysis by Kilpelainen et al. [32], among the 13 established risk alleles for obesity in various genes, only FTO (rs1121980) and MTCH2 (rs10838738) risk alleles were significantly associated with a high birth weight (+11 ± 4 g/allele; p = 0.013; n = 28,219) and low birth weight (−13 ± 5 g/allele; p = 0.012; n = 23,680), respectively.