Significant decrease in serum adiponectin from 2.6 ± 0.09 μg/mL in lean ZSF1 serum to 1.9 ± 0.05 μg/mL in obese ZSF1 serum (p < 0.0001) indicated deposition of newly formed fat and served as a reliable obesity biomarker. This evidence concerns the gene ADIPOQ and obesity due to melanocortin 4 receptor deficiency.