FGF21 and obesity due to melanocortin 4 receptor deficiency: It is possible that the mechanism of selective FGF21 activation in males with SFD-induced obesity was associated withhyperinsulinemia, which was revealed in our work and inthe works of other authors, carried out on rodents consuminghigh-calorie diet (Rodríguez et al., 2003; Priego et al., 2008).An association was found between high plasma insulin andFGF21 levels in obese rodents and humans (Zhang et al.,2008; Chavez et al., 2009), the exact mechanism of which isunknown.