PYY and obesity due to melanocortin 4 receptor deficiency: Obese dams displayed higher fasting plasma leptin, which is produced in proportion to fat mass, and lower peptide-YY (PYY), an appetite-reducing satiety hormone whose blood concentration is decreased in obesity in rats13 and humans12, compared to the lean reference group (leptin: obese 1162.7 ± 67.9 pmol L−1, lean: 749.5 ± 92.8 pmol L−1, P = 0.002; PYY: obese 13.7 ± 0.8 pmol L−1, lean 17.3 ± 1.1 pmol L−1, P = 0.028).