title: Gender differences in the relationships between lean body mass, fat mass and peak bone mass in young adults.
abstract: The relationships between fat mass and bone mass in young adults are unclear. In 1,183 young Australians, lean body mass had a strong positive relationship with total body bone mass in both genders. Fat mass was a positive predictor of total body bone mass in females, with weaker association in males.
  
  
  BACKGROUND
  Body weight and lean body mass are established as major determinants of bone mass, but the relationships between fat mass (including visceral fat) and peak bone mass in young adults are unclear. The aim of this study was to evaluate the associations between bone mass in young adults and three body composition measurements: lean body mass, fat mass and trunk-to-limb fat mass ratio (a surrogate measure of visceral fat).
  
  
  METHODS
  Study participants were 574 women and 609 men aged 19-22 years from the Raine study. Body composition, total body bone mineral content (TBBMC), bone area and areal bone mineral density (TBBMD) were measured using DXA.
  
  
  RESULTS
  In multivariate linear regression models with height, lean body mass, fat mass and trunk-to-limb fat mass ratio as predictor variables, lean mass was uniquely associated with the largest proportion of variance of TBBMC and TBBMD in males (semi-partial R(2) 0.275 and 0.345, respectively) and TBBMC in females (semi-partial R(2) 0.183). Fat mass was a more important predictor of TBBMC and TBBMD in females (semi-partial R(2) 0.126 and 0.039, respectively) than males (semi-partial R(2) 0.006 and 0.018, respectively). Trunk-to-limb fat mass ratio had a weak, negative association with TBBMC and bone area in both genders (semi-partial R(2) 0.004 to 0.034).
  
  
  CONCLUSIONS
  Lean body mass has strong positive relationship with total body bone mass in both genders. Fat mass may play a positive role in peak bone mass attainment in women but the association was weaker in men; different fat compartments may have different effects.
authors.affiliation: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, WA, 6009, Australia, kun.zhu@uwa.edu.au.
authors.forename: K
authors.initials: K
authors.lastname: Zhu
authors.forename: K
authors.initials: K
authors.lastname: Briffa
authors.forename: A
authors.initials: A
authors.lastname: Smith
authors.forename: J
authors.initials: J
authors.lastname: Mountain
authors.forename: A M
authors.initials: AM
authors.lastname: Briggs
authors.forename: S
authors.initials: S
authors.lastname: Lye
authors.forename: C
authors.initials: C
authors.lastname: Pennell
authors.forename: L
authors.initials: L
authors.lastname: Straker
authors.forename: J P
authors.initials: JP
authors.lastname: Walsh
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000273:Adipose Tissue / Q000033:anatomy & histology*; D000886:Anthropometry / Q000379:methods; D001823:Body Composition / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012727:Sex Characteristics; D013851:Thinness / Q000473:pathology; D055815:Young Adult