Related to its role to increase energy expenditure, BAT mass and activity are inversely correlated with obesity and body mass index (Cypess et al., 2009) and certain UCP-1 polymorphisms are associated with obesity and obesity-related conditions (Jia et al., 2010; Chathoth et al., 2018). Here, UCP1 is linked to obesity due to melanocortin 4 receptor deficiency.