Previous studies have investigated irisin and its possible associations with cardiometabolic parameters among both adults and children, with conflicting results; obese patients, patients with diabetes mellitus type 2 and/or patients with metabolic syndrome have been described to have both higher [21,22] and lower irisin levels compared to controls [23,24,25,26,27], while irisin levels have displayed positive, as well as negative associations with adiposity parameters, lipid profile and insulin resistance [21,27,28,29]. Here, FNDC5 is linked to diabetes mellitus.