FNDC5 and obesity due to melanocortin 4 receptor deficiency: For this purpose, 30 obese adults with Prader-Will syndrome (PWS) (age 35.7 ± 1.5 y, BMI 45.5 ± 1.5 kg/m2) and 30 adult controls with common obesity (age 34.9 ± 1.7 y, BMI 46.8 ± 1.4 kg/m2) underwent analysis of irisin levels, metabolic profile, body composition and resting energy expenditure (REE).