FTO and obesity due to melanocortin 4 receptor deficiency: Critically, this positive relation between MMT and sex and age-adjusted BMI z-score held in an adjusted regression model, suggesting unique co-variation above and beyond the influences of sex, age, physical activity, and FTO rs9939609 status – one of the genetic factors most robustly associated with obesity (Frayling et al., 2007; Loos and Yeo, 2014).