For these reasons, physical exercise is a powerful ally in the prevention and improvement of the prognosis of cardiovascular diseases, DM2, and obesity, since it influences the predominance of the secretion of anti-inflammatory myokines, adipokines, and hepatokines, such as irisin, IL-6, IL -15, myonectin, adiponectin, FGF21 (which mitigate the harmful effects of myostatin), TNF-α, resistin, chemerin, fetuin-A, and other cytokines [101]. The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.