Serum FGF-21 levels in patients with fatty liver, obesity, metabolic syndrome and diabetes were significantly higher than those in healthy volunteers (Li et al., 2018; Akour et al., 2017; Li et al., 2010; Keuper, Häring & Staiger, 2019). This evidence concerns the gene FGF21 and obesity due to melanocortin 4 receptor deficiency.