Psychological flexibility as a mediator and mechanism of change in disordered eating: A systematic review

Psychological flexibility (PF) is increasingly considered as a prospective mediator of disordered eating, due to its contextual nature and theoretical association with disordered eating development and maintenance. However, the extent of its efficacy remains unclear. The present study aims to systematically review all available evidence on PF as a unique mediator or mechanism of change in disordered eating, encompassing both cross-sectional and intervention studies. This review followed the Preferred Items for Systematic Reviews and Meta-Analyses (PRISMA) framework throughout. A literature search using PubMed, PsycINFO and Google Scholar databases on cross-sectional and intervention studies was conducted, that identified 19 articles and 27 separate mediation analyses as eligible. PF was found to be a consistent mediator among thirteen risk factors and disordered eating levels in cross-sectional studies, including BMI, body dissatisfaction, self-esteem and external shame. However, the intervention studies showed little confidence for PF to be a successful mechanism of change, potentially due to methodological concerns. The strongest effects were indicated for high-weight individuals and adolescent populations, with weaker indications for males, which has important clinical implications. Future research should improve methodological rigor, as well as refining PF conceptualization and incorporating more positive PF measures.