title: Testing the activitystat hypothesis: a randomised controlled trial.
abstract: It has been hypothesised that an 'activitystat' may biologically regulate energy expenditure or physical activity levels, thereby limiting the effectiveness of physical activity interventions. Using a randomised controlled trial design, the aim of this study was to investigate the effect of a six-week exercise stimulus on energy expenditure and physical activity, in order to empirically test this hypothesis.
  
  
  
  Previously inactive adults (n = 129) [age (mean ± SD) 41 ± 11 year; body mass index 26.1 ± 5.2 kg/m(2)] were randomly allocated to a Control group (n = 43) or a 6-week Moderate (150 min/week) (n = 43) or Extensive (300 min/week) (n = 43) exercise intervention group. Energy expenditure and physical activity were measured using a combination of accelerometry (total counts, minutes spent in moderate to vigorous physical activity) and detailed time use recalls using the Multimedia Activity Recall for Children and Adults (total daily energy expenditure, minutes spent in moderate to vigorous physical activity) at baseline, mid- and end-intervention and 3- and 6-month follow up. Resting metabolic rate was measured at baseline and end-intervention using indirect calorimetry. Analysis was conducted using random effects mixed modeling.
  
  
  
  At end-intervention, there were statistically significant increases in all energy expenditure and physical activity variables according to both accelerometry and time use recalls (p < 0.001) in the Moderate and Extensive groups, relative to Controls. There was no significant change in resting metabolic rate (p = 0.78).
  
  
  
  Taken together, these results show no evidence of an "activitystat" effect. In the current study, imposed exercise stimuli of 150-300 min/week resulted in commensurate increases in overall energy expenditure and physical activity, with no sign of compensation in either of these constructs.
  
  
  
  ACTRN12610000248066  (registered prospectively 24 March 2010).
authors: School of Health Sciences, Alliance for Research in Exercise, Nutrition and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, Australia. s.gomersall1@uq.edu.au.|School of Human Movement and Nutrition Sciences, Centre of Research on Exercise, Physical Activity and Health (CRExPAH), The University of Queensland, Brisbane, Australia. s.gomersall1@uq.edu.au.
authors: S R
authors: SR
authors: Gomersall
authors: School of Health Sciences, Alliance for Research in Exercise, Nutrition and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.
authors: C
authors: C
authors: Maher
authors: School of Health Sciences, Alliance for Research in Exercise, Nutrition and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.
authors: C
authors: C
authors: English
authors: School of Health Sciences, Alliance for Research in Exercise, Nutrition and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.|Diabetes Research Centre, University of Leicester, Leicester General Hospital, Leicester, UK.|NIHR Leicester-Loughborough Diet, Lifestyle and Physical Activity Biomedical Research Unit, Leicester, UK.
authors: A V
authors: AV
authors: Rowlands
authors: School of Health Sciences, Alliance for Research in Exercise, Nutrition and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.
authors: J
authors: J
authors: Dollman
authors: School of Health Sciences, Alliance for Research in Exercise, Nutrition and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.
authors: K
authors: K
authors: Norton
authors: School of Health Sciences, Alliance for Research in Exercise, Nutrition and Activity, Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.
authors: T
authors: T
authors: Olds
mesh_terms: D061725:Accelerometry; D000328:Adult; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005246:Feedback; D005260:Female; D006293:Health Promotion / Q000379:methods*; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome
keywords: Accelerometry; Compensation; Energy expenditure; Physical activity