title: The association between physical activity and reduced body fat lessens with age - results from a cross-sectional study in community-dwelling older adults.
abstract: BACKGROUND
  The aim of this study was to describe the relationship between accelerometer-determined physical activity (PA) and adiposity in community-dwelling older adults. In addition, we were interested in comparing the extent of correlation between questionnaire and accelerometer determined PA.
  
  
  METHODS
  636 community-dwelling older adults (66±7years) were studied. Adiposity was measured using dual-energy X-ray absorptiometry and BMI was calculated. We measured minutes/day spent in sedentary, light, moderate and vigorous intensity activity using both questionnaires and Actigraph GT1M accelerometers.
  
  
  RESULTS
  Participants spent a median of 583(IQR 522-646), 225(176-271), 27(12-45) and 0(0-0) minutes in sedentary, light, moderate and vigorous activities respectively. There was a non linear dose-response inverse relationship between activity intensity and adiposity. After adjusting for age, sex and other levels of PA, for every 10minute increase in activity, total body fat decreased by 169g(95% CI 61-277), 905g(632-1178), and 2208g(759-3657) for light, moderate and vigorous activities respectively. There was an interaction between age and activity; as age increased, the magnitude of the effects of light and moderate activities on adiposity decreased. Sedentary minutes were not associated with adiposity after adjusting for time spent at other PA intensities. Questionnaire measures of PA were weakly correlated with body fat measures when compared to accelerometer determined PA.
  
  
  CONCLUSIONS
  Both the amount and intensity of PA, but not sedentary time, have an independent dose-response association with adiposity. The association is much stronger using objective assessment compared to questionnaire. The magnitude of these associations decrease with age suggesting that physical activity programmes may need to be modified with increasing age.
authors.affiliation: Menzies Research Institute Tasmania, University of Tasmania, Private Bag 23, Hobart, Tasmania 7000, Australia. Electronic address: ycfoong@utas.edu.au.
authors.forename: Yi Chao
authors.initials: YC
authors.lastname: Foong
authors.affiliation: Menzies Research Institute Tasmania, University of Tasmania, Private Bag 23, Hobart, Tasmania 7000, Australia.
authors.forename: Dawn
authors.initials: D
authors.lastname: Aitken
authors.affiliation: Menzies Research Institute Tasmania, University of Tasmania, Private Bag 23, Hobart, Tasmania 7000, Australia.
authors.forename: Tania
authors.initials: T
authors.lastname: Winzenberg
authors.affiliation: Menzies Research Institute Tasmania, University of Tasmania, Private Bag 23, Hobart, Tasmania 7000, Australia.
authors.forename: Petr
authors.initials: P
authors.lastname: Otahal
authors.affiliation: Australian Institute of Musculoskeletal Science, NorthWest Academic Centre, The University of Melbourne, Western Health, St Albans, Victoria 3021, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Scott
authors.affiliation: Menzies Research Institute Tasmania, University of Tasmania, Private Bag 23, Hobart, Tasmania 7000, Australia.
authors.forename: Graeme
authors.initials: G
authors.lastname: Jones
mesh_terms: D061725:Accelerometry / Q000379:methods; D050154:Adiposity / Q000502:physiology*; D000368:Aged; D000375:Aging / Q000502:physiology*; D000886:Anthropometry / Q000379:methods; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D057185:Sedentary Behavior
keywords: Accelerometry; Body composition; Community dwelling; Elderly; Physical activity