This is because syncytin-1 regulates muscle maintenance and regeneration/myogenesis (Frese et al., 2015), and these processes are decreased in obesity (Akhmedov and Berdeaux, 2013; O’Leary et al., 2018), and assuming syncytin-1 has a dominant role in upregulating these processes in skeletal muscle. This evidence concerns the gene ERVW-1 and obesity due to melanocortin 4 receptor deficiency.