title: Examination of mechanisms (E-MECHANIC) of exercise-induced weight compensation: study protocol for a randomized controlled trial.
abstract: BACKGROUND
  Weight loss induced only by exercise is frequently less than expected, possibly because of compensatory changes in energy intake and/or energy expenditure. The purpose of the Examination of Mechanisms (E-MECHANIC) of Exercise-Induced Weight Compensation trial is to examine whether increased energy intake and/or reduced spontaneous activity or energy expenditure (outside of structured exercise) account for the less than expected, exercise-associated weight loss.
  
  
  METHODS
  E-MECHANIC is a three-arm, 6-month randomized (1:1:1) controlled trial. The two intervention arms are exercise doses that reflect current recommendations for (1) general health (8 kcal/kg body weight per week (8 KKW), about 900 kcal/wk) and (2) weight loss (20 KKW, about 2,250 kcal/wk). The third arm, a nonexercise control group, will receive health information only. The sample will include a combined total of 198sedentary, overweight or obese (body mass index: ≥25 kg/m² to ≤45 kg/m²) men and women ages 18 to 65 years. The exercise dose will be supervised and tightly controlled in an exercise training laboratory. The primary outcome variables are energy intake, which will be measured using doubly labeled water (adjusted for change in energy stores) and laboratory-based food intake tests, and the discrepancy between expected weight loss and observed weight loss. Secondary outcomes include changes in resting metabolic rate (adjusted for change in body mass), activity levels (excluding structured exercise) and body composition. In an effort to guide the development of future interventions, the participants will be behaviorally phenotyped and defined as those who do compensate (that is, fail to lose the amount of weight expected) or do not compensate (that is, lose the amount of weight expected or more).
  
  
  CONCLUSIONS
  In this study, we will attempt to identify underlying mechanisms to explain why exercise elicits less weight loss than expected. This information will guide the development of interventions to increase exercise-induced weight loss and maximize weight loss retention and related health benefits.
  
  
  BACKGROUND
  ClinicalTrials.gov ID: NCT01264406 (registration date: 20 December 2010).
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA. candice.myers@pbrc.edu.
authors.forename: Candice A
authors.initials: CA
authors.lastname: Myers
authors.forename: William D
authors.initials: WD
authors.lastname: Johnson
authors.forename: Conrad P
authors.initials: CP
authors.lastname: Earnest
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Rood
authors.forename: Catrine
authors.initials: C
authors.lastname: Tudor-Locke
authors.forename: Neil M
authors.initials: NM
authors.lastname: Johannsen
authors.forename: Shannon
authors.initials: S
authors.lastname: Cocreham
authors.forename: Melissa
authors.initials: M
authors.lastname: Harris
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Church
authors.forename: Corby K
authors.initials: CK
authors.lastname: Martin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001835:Body Weight / Q000502:physiology*; D002149:Energy Intake / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology / Q000628:therapy*; D010101:Oxygen Consumption / Q000502:physiology; D012107:Research Design; D057185:Sedentary Behavior; D015431:Weight Loss / Q000502:physiology*; D055815:Young Adult