Effectiveness of acceptance and commitment therapy for weight stigma and related psychological outcomes: a systematic review protocol

Weight stigma, a pervasive public health concern, is characterized by negative attitudes, prejudices, and stereotypes directed towards individuals with larger body sizes. Empirical evidence indicates a significant association between experiencing weight stigma and adverse psychological health outcomes, including body image dissatisfaction, eating disorders, and increased risk of depression, anxiety, self-harm, and suicidal ideation. Acceptance and Commitment Therapy (ACT), a third-wave behavioral approach, shows potential in reducing weight stigma by targeting psychological flexibility and values-based action. However, current evidence remains limited and fragmented, often neglecting the complex, multidimensional nature of weight stigma. Therefore, this review aims to synthesize and evaluate existing evidence on the effectiveness of ACT in reducing weight stigma and improving related psychological outcomes. Additionally, we will identify the specific content and delivery features of effective ACT interventions targeting weight stigma. We will conduct a comprehensive search of electronic databases, including PubMed, Embase, Web of Science, Scopus, CINAHL, and the Cochrane Library. The Association for Contextual Behavioral Science (ACBS) website will be searched to identify summaries of randomized controlled trials and Google Scholar will be utilized to identify relevant grey literature. Only original research articles published in English from 1994 to 2025 will be included, and the database searches will be updated prior to final manuscript submission to capture the most recent evidence. Screening, data extraction and quality assessment will be conducted independently by the primary reviewer and the second reviewer. Any inconsistencies will be addressed through discussion with a third reviewer. If substantial heterogeneity (I2 > 75%) or insufficient comparable data precludes meta-analysis, findings will be synthesized narratively. This systematic review will synthesize the extant literature on the effectiveness of ACT, encompassing its contents and delivery features in reducing weight stigma and improving related psychological outcomes among individuals experiencing weight-related stigmatization. The evidence generated from this review has the potential to inform public health initiatives, shape future intervention research, and contribute to broader efforts to mitigate the harmful impact of weight stigma on individual and societal levels. PROSPERO CRD420251121507