title: High bone density in adolescents with obesity is related to fat mass and serum leptin concentrations.
abstract: OBJECTIVE
  Obesity has been associated with increased bone mass, but the mechanisms involved are still poorly understood. We aimed to explore the relation between bone mineral density and factors known to influence bone formation in obese and lean adolescents.
  
  
  METHODS
  We recruited 24 obese and 25 lean adolescents in a case-control study. Total body bone mineral density (TB-BMD) z scores and body composition were determined using dual-energy x-ray absorptiometry. We measured 25-hydroxyvitamin D (25-OH-D), glucose, insulin, and leptin concentrations. Physical activity (PA) level was quantified using accelerometer.
  
  
  RESULTS
  TB-BMD z score was higher, whereas 25-OH-D and PA levels were lower in obese compared with lean subjects (TB-BMD z score 1.06 ± 0.96 vs 0.26 ± 0.91, P = 0.004; 25-OH-D 9.9 ± 6.4 vs 18.5 ± 7.4 ng mL, P < 0.001; PA level 308.3 ± 22.1 vs 406.8 ± 29.2 count min, P = 0.01). TB-BMD z score was not related to 25-OH-D or PA levels, but was positively correlated with leptin concentration and fat mass (P < 0.05). Vitamin D concentration was negatively correlated with fat mass (P < 0.001).
  
  
  CONCLUSIONS
  Despite lower serum vitamin D and PA levels, BMD was higher in adolescents with obesity and associated with higher serum leptin concentrations. Furthermore, adolescents with obesity have lower vitamin D serum concentrations than lean controls, probably owing to its distribution in adipose tissue.
authors.affiliation: *Pediatric Sport Medicine and Obesity Care Program, Service of Pediatric Specialties †Pediatric Gastroenterology Unit ‡Pediatric Cardiology Unit, Service of Pediatric Specialties, Department of Child and Adolescent, University Hospitals of Geneva and University of Geneva §Service of Bone Diseases, Department of Rehabilitation and Geriatrics, University Hospitals of Geneva, Geneva, Switzerland.
authors.forename: Albane B R
authors.initials: AB
authors.lastname: Maggio
authors.forename: Dominique C
authors.initials: DC
authors.lastname: Belli
authors.forename: Julie Wacker Bou
authors.initials: JW
authors.lastname: Puigdefabregas
authors.forename: René
authors.initials: R
authors.lastname: Rizzoli
authors.forename: Nathalie J
authors.initials: NJ
authors.lastname: Farpour-Lambert
authors.forename: Maurice
authors.initials: M
authors.lastname: Beghetti
authors.forename: Valérie A
authors.initials: VA
authors.lastname: McLin
mesh_terms: D015502:Absorptiometry, Photon; D061725:Accelerometry; D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D001823:Body Composition; D015992:Body Mass Index; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood*; D008297:Male; D009043:Motor Activity; D009765:Obesity / Q000097:blood / Q000378:metabolism*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D020738:Leptin; D014807:Vitamin D; C104450:25-hydroxyvitamin D