title: Influence of age and gender on fat mass, fat-free mass and skeletal muscle mass among Australian adults: the Australian diabetes, obesity and lifestyle study (AusDiab).
abstract: BACKGROUND
  Bioelectrical impedance (BIA) represents a simple, inexpensive and non-invasive method that is often used to assess fat-mass (FM) and fat-free mass (FFM) in large population-based cohorts.
  
  
  OBJECTIVE
  The aim of this study was to describe the reference ranges and examine the influence of age and gender on FM, FFM and skeletal muscle mass (SMM) as well as height-adjusted estimates of FM [fat mass index (FMI)], FFM [fat-free mass index (FFMI)] and SMM [SMM index (SMI)] in a national, population-based cohort of Australian adults.
  
  
  METHODS
  The analytical sample included a total of 8,582 adults aged 25-91 years of Europid origin with complete data involved in the cross-sectional 1999-2000 Australian, Diabetes, Obesity and Lifestyle (AusDiab) Study.
  
  
  METHODS
  Bioelectrical impedance analysis was used to examine components of body composition. Demographic information was derived from a household interview.
  
  
  RESULTS
  For both genders, FFM, SMM and SMI decreased linearly from the age of 25 years, with the exception that in men SMI was not related to age and FFM peaked at age 38 years before declining thereafter. The relative loss from peak values to ≥75 years in FFM (6-8%) and SMM (11-15%) was similar between men and women. For FM and FMI, there was a curvilinear relationship with age in both genders, but peak values were detected 6-7 years later in women with a similar relative loss thereafter. For FFMI there was no change with age in men and a modest increase in women.
  
  
  CONCLUSIONS
  In Australian adults there is heterogeneity in the age of onset, pattern and magnitude of changes in the different measures of muscle and fat mass derived from BIA, but overall the age-related losses were similar between men and women.
authors.affiliation: Robin M. Daly, Centre for Physical Activity and Nutrition Research, Deakin University, 221 Burwood Highway, Burwood, Melbourne, Australia 3125, Ph: +61-3-9244 6040; Fax: +61-3-9244-6017, E-mail: rmdaly@deakin.edu.au.
authors.forename: C
authors.initials: C
authors.lastname: Strugnell
authors.forename: D W
authors.initials: DW
authors.lastname: Dunstan
authors.forename: D J
authors.initials: DJ
authors.lastname: Magliano
authors.forename: P Z
authors.initials: PZ
authors.lastname: Zimmet
authors.forename: J E
authors.initials: JE
authors.lastname: Shaw
authors.forename: R M
authors.initials: RM
authors.lastname: Daly
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001315:Australia; D001823:Body Composition; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D009765:Obesity; D009929:Organ Size; D012016:Reference Values; D012727:Sex Characteristics; D013997:Time Factors