Objective: To evaluate serum PYY levels in obese adolescents treated in an outpatient obesity treatment program at a public hospital in southern Brazil. Methods: Fifty-one adolescents with obesity were included and followed up for 12 months. They attended 12 consultations with weight loss recommendations based on quantitative and qualitative food goals and reduction of sedentary behavior. Fasting serum levels of PYY, total cholesterol, HDL-cholesterol, triglycerides (TG), LDLcholesterol (LDL-C), insulin and glycemia were collected in T0 (before the first consultation), T1 (after 24 weeks) and T2 (after 48 weeks). Besides blood samples, abdominal circumference (AC) was measured, and the homeostasis model assessment (HOMA-IR) was calculated. By electrical bioimpedance analysis, fat mass and basal metabolic rate were measured. Results: Between T0 and T2, there was weight loss with a significant reduction of body mass index (BMI) Z-scores (p
