title: Free-living activity energy expenditure in women successful and unsuccessful at maintaining a normal body weight.
abstract: BACKGROUND
  Although physical inactivity is believed to contribute to the rising prevalence of obesity, the role and magnitude of its contribution to weight gain are unknown.
  
  
  OBJECTIVE
  We compared total free-living activity energy expenditure (AEE) and physical activity level in women successful and unsuccessful at maintaining a normal body weight.
  
  
  METHODS
  Premenopausal, generally sedentary women were studied at their normal weight and 1 y later after no intervention. Two groups were identified on the basis of extreme weight changes: maintainers (n = 27) had a weight gain of less-than-or-equal 3% of their initial body weight ( less-than-or-equal 2 kg/y) and gainers (n = 20) had a weight gain of >10% (>6 kg/y). At baseline and follow-up, evaluations were conducted during 4 wk of diet-controlled, energy-balance conditions. Free-living AEE and physical activity were assessed with the use of doubly labeled water, exercise energy economy and muscle strength with the use of standardized exercise tests, and sleeping EE and substrate utilization with the use of chamber calorimetry.
  
  
  RESULTS
  Maintainers lost a mean (plus minusSD) of 0.5 plus minus 2.2 kg/y and gainers gained 9.5 plus minus 2.1 kg/y. Gainers had a lower AEE (P < 0.02), a lower physical activity level (P < 0.01), and less muscle strength (P < 0.001); these differences between groups remained significant from baseline to follow-up. Sleeping EE, exercise economy, and sleeping or 24-h substrate utilization were not significantly different between the 2 groups. A lower AEE in the gainers explained approximately 77% of their greater weight gain after 1 y.
  
  
  CONCLUSIONS
  The general US population should increase their daily physical activity levels to decrease the rising prevalence of obesity.
authors.affiliation: Department of Nutrition Sciences, the University of Alabama at Birmingham, 35294, USA. weinsier@shrp.uab.edu
authors.forename: Roland L
authors.initials: RL
authors.lastname: Weinsier
authors.forename: Gary R
authors.initials: GR
authors.lastname: Hunter
authors.forename: Renée A
authors.initials: RA
authors.lastname: Desmond
authors.forename: Nuala M
authors.initials: NM
authors.lastname: Byrne
authors.forename: Paul A
authors.initials: PA
authors.lastname: Zuckerman
authors.forename: Betty E
authors.initials: BE
authors.lastname: Darnell
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D002153:Calorimetry, Indirect; D004038:Diet, Reducing; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000209:etiology* / Q000378:metabolism / Q000517:prevention & control; D011446:Prospective Studies; D011865:Radioisotope Dilution Technique