Peptide YY is a regulator of energy homeostasis in obese children before and after weight loss.

CONTEXT: The gut hormone peptide YY(3-36) (PYY) reduces food intake via hypothalamic Y2 receptors in the brain. There is not much known about PYY in obese children.

OBJECTIVE: The objective of this study was to investigate the role of PYY in the metabolic changes in obese children and its change during weight loss.

SETTING: The study was performed at a university medical center.

PARTICIPANTS: We studied 73 obese children and 45 age-matched normal-weight children.

INTERVENTIONS: We determined fasting serum total PYY and leptin by RIA in obese and normal-weight children. Fasting PYY was also measured in 28 obese children before and after completion of a 1-yr outpatient weight reduction program.

MAIN OUTCOME MEASURES: PYY, insulin, and body mass index were the main outcome measures.

RESULTS: Obese children demonstrated significantly lower PYY levels than lean children (median, 67 vs. 124 pg/ml; P < 0.001). Fasting PYY correlated negatively to the degree of overweight. PYY levels did not differ significantly between boys and girls, nor between prepubertal and pubertal children. The group of patients participating in the outpatient weight reduction program was divided into four quartiles according to their changes in body mass index SD score over a 1-yr period. PYY increased significantly in patients with the most effective weight loss, but decreased in the subgroup of children with weight gain.

CONCLUSIONS: PYY is negatively correlated to the degree of overweight, with reduced values in obese compared with normal-weight children. Decreased PYY levels could predispose subjects to develop obesity. Our results indicate that low pretreatment PYY levels that increase during weight loss may be a predictor of maintained weight loss.