Given the critical role of fetuin-A in insulin resistance, obesity, T2D, and MASLD, and the beneficial effects of adiponectin on fatty acid oxidation, lipid reduction, and improvement of insulin resistance through activation of 5′-AMP-activated protein kinase (pAMPK), it is not surprising that adiponectin and fetuin-A serum concentrations are inversely correlated in these diseases. This evidence concerns the gene ADIPOQ and obesity due to melanocortin 4 receptor deficiency.