title: Association of run-in periods with weight loss in obesity randomized controlled trials.
abstract: Study-level design characteristics that inform the optimal design of obesity randomized controlled trials (RCTs) have been examined in few studies. A pre-randomization run-in period is one such design element that may influence weight loss. We examined 311 obesity RCTs published between 1 January 2007 and 1 July 2009 that examine d weight loss or weight gain prevention as a primary or secondary end-point. Variables included run-in period, pre-post intervention weight loss, study duration (time), intervention type, percent female and degree of obesity. Linear regression was used to estimate weight loss as a function of (i) run-in (yes/no) and (ii) run-in, time, percent female, body mass index and intervention type. Interaction terms were also examined. Approximately 19% (18.6%) of the studies included a run-in period, with pharmaceutical studies having the highest frequency. Although all intervention types were associated with weight loss (Mean = 2.80 kg, SD = 3.52), the inclusion of a pre-randomization run-in was associated with less weight loss (P = 0.0017) compared with studies that did not include a run-in period. However, this association was not consistent across intervention types. Our results imply that in trials primarily targeting weight loss in adults, run-in periods may not be beneficial for improving weight loss outcomes in interventions.
authors.affiliation: Department of Epidemiology, 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: O
authors.initials: O
authors.lastname: Affuso
authors.forename: K A
authors.initials: KA
authors.lastname: Kaiser
authors.forename: T L
authors.initials: TL
authors.lastname: Carson
authors.forename: K H
authors.initials: KH
authors.lastname: Ingram
authors.forename: M
authors.initials: M
authors.lastname: Schwiers
authors.forename: H
authors.initials: H
authors.lastname: Robertson
authors.forename: F
authors.initials: F
authors.lastname: Abbas
authors.forename: D B
authors.initials: DB
authors.lastname: Allison
mesh_terms: D000328:Adult; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology / Q000517:prevention & control*; D018579:Patient Selection; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D017678:Sex Distribution; D015430:Weight Gain; D015431:Weight Loss
keywords: Obesity; randomized clinical trials; run-in periods