In the mitochondrial ATP synthase membrane subunit 6 (MT-ATP6) gene, essential for OXPHOS, two exonic variants (MT:8684C>T and MT:8664A>G) were found to associate positively with obesity risk, and one exonic variant (MT:8994G>A) was unique to the obese group. This evidence concerns the gene MT-ATP6 and obesity due to melanocortin 4 receptor deficiency.