title: Body composition and bone health in adolescents after Roux-en-Y gastric bypass for severe obesity.
abstract: Laparoscopic Roux-en-Y gastric bypass (RYGB) causes changes in body composition and bone metabolism, yet little is known about effects in adolescents.
  
  
  
  The objective of this study was to report dual-energy X-ray absorptiometry measures and serum bone markers, hypothesizing that bone turnover increases after surgery.
  
  
  
  Inclusion criteria included the following: age 13-18 years and body mass index (BMI) >35 kg/m2. Seventy-two adolescents (22 boys; mean age 16.5 years; BMI 44.8 kg/m2) undergoing RYGB underwent dual-energy X-ray absorptiometry and serum bone marker analyses preoperatively and annually for 2 years.
  
  
  
  Mean BMI reduction at 2 years was 15.1 kg/m2. Body composition changes included a reduction in fat mass (51.8% to 39.6%, p < 0.001) and relative increase in lean mass (47.0% to 58.1%, p < 0.001). In contrast to previous studies in adults, adolescent boys lost a greater percentage of their body fat than girls (-17.3% vs. -9.5%, p < 0.001). Individual bone mineral density Z-scores (BMD-Z) at baseline were within or above the normal range. The mean (SD) BMD-Z was 2.02 (1.2) at baseline, decreasing to 0.52 (1.19) at 2 years. Higher concentrations of serum CTX (p < 0.001) and osteocalcin (p < 0.001) were observed in boys throughout the study period. Levels rose in the first year, before decreasing modestly in the second. Levels of serum markers of bone synthesis and resorption were higher in boys, whose skeletal maturity occurs later than girls'.
  
  
  
  Differences in body fat and lean mass proportions were observed according to sex following RYGB. Bone turnover increased, and BMD decreased to levels approaching a norm for age. Long-term outcome will determine the clinical relevance.
authors.affiliation: Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, the University of Gothenburg, Gothenburg, Sweden.|Department of Research, Royal College of Surgeons of England, Lincoln's Inn Fields, London, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Beamish
authors.affiliation: Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, the University of Gothenburg, Gothenburg, Sweden.|Department of Pediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, the University of Gothenburg, Gothenburg, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Gronowitz
authors.affiliation: Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, the University of Gothenburg, Gothenburg, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Olbers
authors.affiliation: Childhood Obesity Unit, Skåne University Hospital, Malmö, Sweden.
authors.forename: C-E
authors.initials: CE
authors.lastname: Flodmark
authors.affiliation: Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Marcus
authors.affiliation: Department of Pediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, the University of Gothenburg, Gothenburg, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Dahlgren
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D001823:Body Composition; D015992:Body Mass Index; D015519:Bone Density; D005260:Female; D005500:Follow-Up Studies; D015390:Gastric Bypass / Q000009:adverse effects*; D006801:Humans; D008297:Male; D009767:Obesity, Morbid / Q000601:surgery*; D015431:Weight Loss
chemical_list: D015415:Biomarkers
keywords: Adolescent; bariatric surgery; bone; gastric bypass; obesity; paediatric