In order to address the epidemic of childhood obesity, to predict the risk of development of cardiometabolic abnormalities, and to evaluate the response to lifestyle and therapeutic interventions, novel biomarkers, such as Irisin and Fibroblast Growth Factor 21 (FGF-21), have been proposed as prognostic and diagnostic markers in adults and children with overweight and obesity [8,9,10,11,12,13,14,15,16,17,18,19,20]. The gene discussed is FGF21; the disease is obesity disorder.