GDF15 and obesity due to melanocortin 4 receptor deficiency: However, when analysing only the cohort of patients with obesity, circulating GDF15 levels maintain positive correlations with weight and BMI, but showed a negative correlation with body fat percentage, indicating that GDF15 levels are inversely associated with adiposity within the obese population, suggesting that elevated circulating GDF15 levels may confer some protection against fat accumulation in individuals with obesity.