title: Rigorous control conditions diminish treatment effects in weight loss-randomized controlled trials.
abstract: It has not been established whether control conditions with large weight losses (WLs) diminish expected treatment effects in WL or prevention of weight gain (PWG)-randomized controlled trials (RCTs).
  
  
  
  We performed a meta-analysis of 239 WL/PWG RCTs that include a control group and at least one treatment group. A maximum likelihood meta-analysis framework was used to model and understand the relationship between treatment effects and control group outcomes.
  
  
  
  Under the informed model, an increase in control group WL of 1 kg corresponds with an expected shrinkage of the treatment effect by 0.309 kg (95% confidence interval (-0.480, -0.138), P=0.00081); this result is robust against violations of the model assumptions.
  
  
  
  We find that control conditions with large WLs diminish expected treatment effects. Our investigation may be helpful to clinicians as they design future WL/PWG studies.
authors.affiliation: Department of Nutritional Sciences, College of Human Sciences, Texas Tech University, Lubbock, TX, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Dawson
authors.affiliation: Office of Energetics, School of Public Health, University of Alabama at Birmingham, Birmingham, AL, USA.|Nutrition Obesity Research Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Kaiser
authors.affiliation: Nutrition Obesity Research Center, University of Alabama at Birmingham, Birmingham, AL, USA.|Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: O
authors.initials: O
authors.lastname: Affuso
authors.affiliation: Section on Research Methods and Clinical Trials, Department of Biostatistics, School of Public Health, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Cutter
authors.affiliation: Office of Energetics, School of Public Health, University of Alabama at Birmingham, Birmingham, AL, USA.|Nutrition Obesity Research Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Allison
mesh_terms: D006801:Humans; D009765:Obesity / Q000517:prevention & control*; D016032:Randomized Controlled Trials as Topic / Q000379:methods* / Q000592:standards*; D016896:Treatment Outcome; D015431:Weight Loss; D061217:Weight Reduction Programs