The obesity-associated protein FTO, the first identified m6A demethylase in animals, catalyzes demethylation by sequentially oxidizing m6A to unstable intermediates, hm6A and f6A, followed by the removal of one molecule of formaldehyde and formic acid, respectively, ultimately reverting to adenine (A) [54]. The gene discussed is FTO; the disease is obesity due to melanocortin 4 receptor deficiency.