title: Relationship of obesity with osteoporosis.
abstract: BACKGROUND
  The relationship between obesity and osteoporosis has been widely studied, and epidemiological evidence shows that obesity is correlated with increased bone mass. Previous analyses, however, did not control for the mechanical loading effects of total body weight on bone mass and may have generated a confounded or even biased relationship between obesity and osteoporosis.
  
  
  OBJECTIVE
  The objective of this study was to reevaluate the relationship between obesity and osteoporosis by accounting for the mechanical loading effects of total body weight on bone mass.
  
  
  METHODS
  We measured whole body fat mass, lean mass, percentage fat mass, body mass index, and bone mass in two large samples of different ethnicity: 1988 unrelated Chinese subjects and 4489 Caucasian subjects from 512 pedigrees. We first evaluated the Pearson correlations among different phenotypes. We then dissected the phenotypic correlations into genetic and environmental components with bone mass unadjusted or adjusted for body weight. This allowed us to compare the results with and without controlling for mechanical loading effects of body weight on bone mass.
  
  
  RESULTS
  In both Chinese and Caucasian subjects, when the mechanical loading effect of body weight on bone mass was adjusted for, the phenotypic correlation (including its genetic and environmental components) between fat mass (or percentage fat mass) and bone mass was negative. Further multivariate analyses in subjects stratified by body weight confirmed the inverse relationship between bone mass and fat mass, after mechanical loading effects due to total body weight were controlled.
  
  
  CONCLUSIONS
  Increasing fat mass may not have a beneficial effect on bone mass.
authors.affiliation: Department of Orthopedic Surgery, School of Medicine, University of Missouri-Kansas City, 2411 Holmes Street, Kansas City, MO 64108, USA.
authors.forename: Lan-Juan
authors.initials: LJ
authors.lastname: Zhao
authors.forename: Yong-Jun
authors.initials: YJ
authors.lastname: Liu
authors.forename: Peng-Yuan
authors.initials: PY
authors.lastname: Liu
authors.forename: James
authors.initials: J
authors.lastname: Hamilton
authors.forename: Robert R
authors.initials: RR
authors.lastname: Recker
authors.forename: Hong-Wen
authors.initials: HW
authors.lastname: Deng
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001696:Biomechanical Phenomena; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D002681:China / Q000453:epidemiology; D005006:Ethnicity; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D009929:Organ Size / Q000502:physiology; D010024:Osteoporosis / Q000150:complications* / Q000503:physiopathology; D010641:Phenotype; D012727:Sex Characteristics; D014481:United States / Q000453:epidemiology; D044465:White People