Our data indicated an increase in circulating irisin le-vels in patients with class 1and 2 obesity (Group 2) but not in those with class 3 obesity (Group 3).Additionally, irisin levels were inversely correlated with anthropometricmeasurements (body weight and waist circumference) and metabolic parameters (plasmaglucose, HbA1c, and triglycerides). The gene discussed is FNDC5; the disease is obesity due to melanocortin 4 receptor deficiency.