Those with the greatest increase in irisin (Tertile 3) had significantly higher odds of obesity (OR 2.39, 95% CI 1.24–4.71), abdominal obesity (OR 2.19, 95% CI 1.04–4.72), sarcopenia (OR 2.11, 95% CI 1.14–3.97), sarcopenic obesity (OR 3.40, 95% CI 1.43–8.61) and low ALST (OR 2.21, 95% CI 1.24–3.99) compared to Tertile 1 after full adjustment. Here, FNDC5 is linked to obesity due to melanocortin 4 receptor deficiency.