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 January 1, 2007 and July 1, 2009 that examined weight loss or weight gain prevention as a primary or secondary endpoint. 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 1) run-in (yes/no), and 2) run-in, time, percent female, body mass index, intervention type. Interaction terms were also examined. Approximately nineteen percent (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 to 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.

Outcome of a psychosocial health promotion intervention aimed at improving physical health and reducing alcohol use in patients with schizophrenia and psychotic disorders (MINT)

“…A review of 311 weight loss studies showed that only 19% of the studies included a run-in period; the highest frequency was found in pharmaceutical studies. The inclusion of a pre-randomization run-in period was associated with less weight loss (P = 0.0017) than the absence of a run-in period (Affuso et al, 2014). However, the multi-component design of the intervention was also a weakness.…”

“…Even so, weight change during the prerandomization (run-in) phase is rarely reported in obesity or other types of health promotion trials (West et al, 2011). Only 19% of the interventions included in a meta-analysis of 311 obesity RCTs included a run-in period, and most of these were trials of pharmaceuticals (Affuso et al, 2014), possibly because the U.S. Food and Drug Administration's 1996…”

Rigorous control conditions diminish treatment effects in weight loss-randomized controlled trials

“…Additionally, very rigorous methods were used to select studies, extract the data and assure completeness and accuracy of the dataset; for example, three rounds of inter-rater reliability were performed when assessing study characteristics and data, to ensure agreement at or above 80% (ref. 4). While some differences in adjusted weight loss may be observed between different types of interventions (e.g., diet plus exercise typically having a greater effect on weight loss, versus exercise alone), the range of effects outside of bariatric surgery (not included in this analysis) is not large.…”

“…This meta-analysis was performed as a secondary analysis to another investigation 4 ; as it uses publically available summary data, these projects received a certificate of exemption from the University of Alabama at Birmingham Institutional Review Board in accordance with the Common Rule. The review criteria here are slightly changed from that previous investigation, so we provide the relevant details below:…”

“…Additionally, missing data exist for both means and standard deviations of weight change within study arms 4 . Thus, we performed multiple imputation using SPSS version 20 (ref.…”