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]. Here, FGF21 is linked to Obesity.