title: Discordance between fat mass index and body mass index is associated with reduced bone mineral density in women but not in men: the Busselton Healthy Ageing Study.
abstract: The obesity-BMD relationship is complex. In 3045 middle-aged adults, we found that in women (but not men) with discordant fat mass index (FMI)/BMI categories, higher body fat for BMI was associated with lower BMD, suggesting that increased fat mass without an accompanying increase in lean mass may be deleterious to bone.
  
  
  
  The relationship between obesity and BMD is complex. FMI (fat mass (kg) / height (m)2) is a more accurate measure of fatness than BMI, and depending on body composition, some individuals have discordant BMI/FMI categories. We examined associations between FMI, BMI and BMD in participants in the Busselton Healthy Ageing Study.
  
  
  
  Body composition and BMD of the hip, spine and total body were measured using DXA in 3045 participants (1644 females) aged 45-67 years. Using standard BMI/FMI categories, the participants were classified as underweight/fat deficit, normal, overweight/excess fat, obese I and obese II-III.
  
  
  
  BMI and FMI categories were concordant in 77.3 % of females and 71.2 % of males. There were 12.9 % females and 13.2 % males in a higher FMI than BMI category (high body fat for BMI), whereas 9.8 % females and 15.6 % males were in a lower category (low body fat for BMI). Females with high body fat for BMI had significantly lower covariate-adjusted BMD at the femoral neck, total hip and total body (differences of 3.8, 5.1 and 2.6 %, respectively, all P < 0.05) than females with low body fat for BMI and lower total body BMD than women with concordant FMI/BMI (by 1.4 %, P = 0.04). In males, BMD did not differ significantly between those who were concordant or discordant for FMI/BMI categories.
  
  
  
  In women (but not men) with discordant FMI/BMI categories, higher body fat for BMI was associated with lower BMD, suggesting that increased fat mass without an accompanying increase in lean mass may be deleterious to bone.
authors.affiliation: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, WA, 6009, Australia. kun.zhu@uwa.edu.au.|School of Medicine and Pharmacology, University of Western Australia, Crawley, WA, Australia. kun.zhu@uwa.edu.au.
authors.forename: K
authors.identifier: 0000-0002-8723-7574
authors.initials: K
authors.lastname: Zhu
authors.affiliation: Busselton Population Medical Research Institute, Busselton, WA, Australia.|School of Population Health, University of Western Australia, Crawley, WA, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Hunter
authors.affiliation: School of Medicine and Pharmacology, University of Western Australia, Crawley, WA, Australia.|Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, Nedlands, WA, Australia.
authors.forename: A
authors.initials: A
authors.lastname: James
authors.affiliation: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, WA, 6009, Australia.|Department of Clinical Biochemistry, PathWest Laboratory Medicine, Queen Elizabeth II Medical Centre, Nedlands, WA, Australia.
authors.forename: E M
authors.initials: EM
authors.lastname: Lim
authors.affiliation: Department of Clinical Biochemistry, Fiona Stanley Hospital, Murdoch, WA, Australia.
authors.forename: B R
authors.initials: BR
authors.lastname: Cooke
authors.affiliation: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, WA, 6009, Australia.|School of Medicine and Pharmacology, University of Western Australia, Crawley, WA, Australia.
authors.forename: J P
authors.initials: JP
authors.lastname: Walsh
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000273:Adipose Tissue / Q000033:anatomy & histology* / Q000502:physiology; D000368:Aged; D000886:Anthropometry / Q000379:methods; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D005260:Female; D000073656:Healthy Aging / Q000502:physiology; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology; D050177:Overweight / Q000503:physiopathology; D012727:Sex Characteristics
keywords: Baby boomers; Body mass index; Bone mineral density; Busselton Healthy Ageing Study; Fat mass index; Middle-aged adults