title: Sex difference in the effect of puberty on the relationship between fat mass and bone mass in 926 healthy subjects, 6 to 18 years old.
abstract: OBJECTIVE
  Understanding factors influencing bone mineral accrual is critical to optimize peak bone mass during childhood. The epidemic of pediatric obesity and reported higher incident of fracture risk in obese children led us to study the influence of fat mass on bone mineral content (BMC) in children.
  
  
  METHODS
  Height; weight; pubertal stage; and BMC, non-bone fat-free mass (nbFFM), and fat mass (FM) by DXA were obtained in a multiethnic group of healthy children (444 girls/482 boys; 6 to 18 years old) recruited in the New York metropolitan area. Regression techniques were used to explore the relationship between BMC and FM, with age, height, nbFFM, pubertal stage, sex, and ethnicity as covariates.
  
  
  RESULTS
  Because there were significant sex interactions, separate regression analyses were performed for girls and boys. Although ln(nbFFM) was the greatest predictor of ln(BMC), ln(FM) was also a significant predictor in prepubertal boys and all girls but not in pubertal boys. This effect was independent of ethnicity.
  
  
  CONCLUSIONS
  FM was a determinant of BMC in all girls but in only prepubertal boys. Our study confirms nbFFM as the greatest predictor of BMC but is the first to find a sex difference in the effect of puberty on the relationship of FM to BMC. Our results suggest that, in two individuals of the same sex and weight, the one with greater fat mass will have lower BMC, especially pubertal boys. The implications of these findings for achievement of optimal peak bone mass in a pediatric population with an unprecedented incidence of overweight and "overfat" status remain to be seen.
authors.affiliation: Body Composition Unit, St. Luke's-Roosevelt Hospital Center, New York, New York, USA.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ackerman
authors.forename: John C
authors.initials: JC
authors.lastname: Thornton
authors.forename: Jack
authors.initials: J
authors.lastname: Wang
authors.forename: Richard N
authors.initials: RN
authors.lastname: Pierson
authors.forename: Mary
authors.initials: M
authors.lastname: Horlick
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity / Q000208:ethnology / Q000502:physiology*; D000293:Adolescent; D001741:Black or African American / Q000706:statistics & numerical data; D000704:Analysis of Variance; D044466:Asian People / Q000706:statistics & numerical data; D001827:Body Height / Q000208:ethnology / Q000502:physiology; D001835:Body Weight / Q000208:ethnology / Q000502:physiology; D015519:Bone Density / Q000502:physiology*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D009518:New York; D011627:Puberty / Q000208:ethnology / Q000502:physiology*; D012737:Sex Factors; D044465:White People / Q000706:statistics & numerical data