title: Energy balance in a respiration chamber: individual adjustment of energy intake to energy expenditure.
abstract: OBJECTIVE
  In studies on substrate utilization, a state of energy balance is often required. Energy requirements are based on measured or calculated sleeping metabolic rate (SMR) or basal metabolic rate (BMR). A study was performed to compare this protocol with adjustment of energy intake (EI) to 24 h energy expenditure (24 h EE).
  
  
  METHODS
  In part one, eight subjects spent one night and the subsequent three days in a respiration chamber. On day 1 EI was set at 1.5*SMR. On day 2 and 3 EI was set at 24 h EE of day 1. In part two of the study, an activity protocol was provided while staying in the chamber. 12 subjects spent one night and the subsequent two days in the respiration chamber. On day 1 EI was set at 1.55*SMR and on day 2 EI was set at 24 h EE of day 1.
  
  
  METHODS
  Sleeping metabolic rate, diet induced thermogenesis, physical activity index and 24 h expenditure were measured using a respiration chamber.
  
  
  METHODS
  Eight healthy normal-weight females (age: 22 +/- 3, BMI: 20.9 +/- 1.8) in part one and twelve healthy normal-weight males and females (age: 26 +/- 2, BMI: 21.4 +/- 0.5) in part two of the study.
  
  
  RESULTS
  Physical activity index (PAI = 24 h EE/SMR) on day 1 (part 1) was 1.55 +/- 0.04, close to the predicted value of 1.5, but between-subject variation was large (range: 1.39-1.68). Absolute deviation from energy balance reduced significantly from 1.35 +/- 0.30 MJ/d on day 1 to 0.51 +/- 0.21 and 0.31 +/- 0.10 MJ/d on day 2 and 3 respectively (P < 0.05). The latter can be considered as near to energy balance. With the activity protocol (part 2) absolute deviation from energy balance reduced significantly from 0.93 +/- 0.20 MJ/d on day 1 to 0.27 +/- 0.11 MJ/d on day 2 (P < 0.05).
  
  
  CONCLUSIONS
  A three day stay in the chamber allows adjustment of energy intake to energy expenditure, in this way achieving a state close to energy balance. When prescribing an activity protocol the same results can be obtained within two days.
authors.affiliation: Department of Human Biology, Maastricht University, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: Schrauwen
authors.forename: W D
authors.initials: WD
authors.lastname: van Marken Lichtenbelt
authors.forename: K R
authors.initials: KR
authors.lastname: Westerterp
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001273:Atmosphere Exposure Chambers; D002153:Calorimetry, Indirect; D002940:Circadian Rhythm / Q000502:physiology*; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D013997:Time Factors