FNDC5 and obesity due to melanocortin 4 receptor deficiency: Participants in the highest irisin tertile had significantly higher odds of obesity (odds ratio [OR] 1.85, 95% CI 1.03–3.35), abdominal obesity (OR 1.82, 95% CI 1.06–3.14) and sarcopenic obesity (OR 2.59, 95% CI 1.18–5.97) compared to the lowest tertile in Model 2.