Many studies have revealed no significant increase in levels of UCP1 and/or FGF21 (Fibroblast growth factor 21) in BAT, although the dose of n−3 PUFAs requisite for exerting an anti-obesity effect was increased threefold (Kuda et al., 2018). The gene discussed is UCP1; the disease is obesity due to melanocortin 4 receptor deficiency.