A meta-analytic review of impact of measurement choice on RCTs to reduce appearance internalization

Prior reviews have shown that interventions targeting internalization of appearance standards are generally efficacious, though there is considerable heterogeneity in estimates across studies. This updated review of the literature evaluates whether efficacy estimates from RCTs systematically vary as a function of three related outcome measures (internalization, awareness, and perceived pressure regarding appearance standards).

Seven electronic databases were systematically searched from inception to February 8, 2023. The Cochrane Risk of Bias tool assessed each study's risk of bias. Studies included were randomized-controlled trials evaluating body image/eating disorder prevention or intervention programs targeting internalization as a focal point of treatment. Effect sizes were meta-analyzed and meta-regression analyses were conducted investigating the impact of outcome measure choice on study effect size at post-intervention and follow-up.

Thirty-seven studies (N = 4809 participants) were included. The meta-analytic findings as expected found interventions efficacious at reducing internalization post-intervention (d = -0.47, 95% CI [-0.60 to -0.34], k = 44), and at follow-up (d = -0.28, 95% CI [-0.39 to -0.17], k = 43), but also highly heterogenous (I²  = 52-67%). Operationalization of internalization moderated results at follow-up but not post-intervention timepoints, with awareness measures (compared with internalization measures) producing weaker effect sizes. Exploratory analyses found bigger effects when internalization was compared with all other measurement categories combined, suggesting possible issues with statistical power in main analyses.

Mixed present findings suggest need for further evaluation of measurement effects on efficacy, and possible caution in choice of outcome measure for internalization-based interventions.

This review provides some preliminary evidence that choice of survey measures used in randomized controlled trials can impact our judgments about whether a trial reduces the extent to which participants endorse unrealistic appearance standards. Accuracy in measurement of this efficacy of trials is crucial, given the role that internalized appearance standards play in onset and maintenance of eating disorders.