Psychological Interventions for Internalized Weight Stigma: A Systematic Review of Feasibility, Acceptability, and Preliminary Efficacy

Background Internalized weight stigma (IWS) is highly prevalent and associated with deleterious mental and physical health outcomes. Initiatives are needed to address IWS and promote effective coping and resilience among individuals who are exposed to weight stigma. We conducted a systematic review of psychological interventions for IWS and examined their feasibility, acceptability, and preliminary efficacy at reducing IWS and related negative physiological and psychological health outcomes. Methods Eight databases were searched. Inclusion criteria included: (1) psychological intervention; (2) published in English; and (3) included internalized weight stigma as an outcome. Exclusion criteria included: (1) commentary or review; and (2) not a psychological intervention. A systematic narrative review framework was used to synthesize results. Results Of 161 articles screened, 20 were included. Included interventions demonstrated high feasibility, acceptability, and engagement overall. Sixteen of 20 included studies observed significant reductions in IWS that were maintained over follow-up periods, yet data on whether interventions produced greater reductions than control conditions were mixed. Studies observed significant improvements in numerous physical and mental health outcomes. Conclusions Findings indicate that existing interventions are feasible, acceptable, and may provide meaningful improvements in IWS and associated health outcomes, highlighting the potential for psychological interventions to promote improved health and wellbeing in individuals with IWS. Additional research using rigorous study designs (e.g., randomized controlled trials) is needed to further evaluate the efficacy of interventions for IWS.

potential for psychological interventions to promote improved health and wellbeing in individuals with IWS.

Background
Decades of research have documented that weight stigma (i.e., the societal devaluation and mistreatment of individuals that results from negative attitudes, beliefs, and stereotypes based on weight) is a global public health concern (1)(2)(3).Experiences of weight stigma and discrimination, which are widespread in employment and health care settings (4)(5)(6)(7), are robustly associated with a myriad of adverse physiological outcomes (e.g., increased diabetes risk, dysregulated cortisol, oxidative stress) and mental health issues (e.g., depression, disordered eating, low self-esteem) (8,9).Longitudinal research has also implicated weight stigma as a contributing factor to the maintenance of obesity and related diseases (10,11).Individuals often internalize the pervasive negative stereotypes based on weight (e.g., that individuals with higher weight are lazy or lack willpower), resulting in internalized weight stigma (IWS) (12,13), also referred to as "weight self-stigma" or "weight bias internalization."An estimated 40-50% of U.S. adults with higher weight have IWS (14).IWS is associated with negative mental and physical health outcomes, including depression, chronic stress, and disordered eating (15)(16)(17)(18) and has been linked to healthcare avoidance (6, 19).Initiatives are needed to address IWS and its deleterious effects on physical and mental health and to promote coping and resilience among individuals who experience weight stigma.
Although public health campaigns and policies to reduce weight stigma have been introduced and evaluated (20,21), strategies for addressing IWS have received less attention.Research on strategies for reducing mental health self-stigma suggests that psychological interventions aimed at reducing IWS represent a promising approach for changing individuals' self-stigmatizing beliefs, increasing selfesteem and empowerment, and promoting effective coping (22).In recent years, numerous studies developing and evaluating novel psychological interventions to address IWS have aimed to elucidate the potential for these interventions to reduce IWS and associated mental and physical health outcomes.It has also been proposed that intervention components targeting IWS may be integrated into lifestyle modi cation interventions to improve individuals' ability to engage in behavioral lifestyle changes, given that IWS is associated with shame and poor self-e cacy, which may interfere with these abilities (23)(24)(25).
No study to date has reviewed psychological interventions for IWS and associated health outcomes.As such, we conducted a systematic review to synthesize studies examining components of existing interventions, their feasibility and acceptability, and their preliminary e cacy at reducing IWS and related negative physiological and psychological health outcomes.As research in this area is limited, we

Inclusion and Exclusion Criteria
Identi ed articles were screened based on the following inclusion criteria: (1) Psychological intervention (e.g., acceptance and commitment therapy, cognitive-behavioral therapy, self-compassion therapy); (2) Published in English; and (3) Included a measure of internalized weight stigma or bias as an intervention outcome.
Identi ed studies were excluded based on the following exclusion criteria: (1) Commentary or review paper; (2) Not a psychological intervention (e.g., public health campaigns to reduce weight stigma); and (3) Interventions aimed to reduce weight stigmatizing attitudes in healthcare professionals.

Data Extraction and Synthesis
Identi ed articles were uploaded into Covidence systematic review software.Article titles and abstracts were independently screened for relevance by the rst four authors.Two authors each conducted full text reviews and consulted with one another to resolve con icts.
The following information was extracted from the articles: year of publication, country, study design, sample characteristics (e.g., sample size, demographics, weight, baseline IWS), type of psychological intervention evaluated, and data on the primary outcome of interest (i.e., IWS) and other relevant psychosocial or physiological health outcomes assessed (e.g., body image, weight, disordered eating behaviors, self-compassion, depression) following the intervention.

Results
Article Selection A total of 161 articles identi ed in the search following the removal of duplicates were screened, of which 106 were excluded from full-text review.Of the 57 full texts assessed for eligibility, 32 were excluded for the following reasons: Protocol paper (n = 10), not a full-length manuscript (n = 7), wrong study design (n = 5), wrong outcome measures (n = 7), unpublished manuscript (n = 3), wrong patient population (n = 1), wrong intervention type (n = 1), and not in English (n = 1).Thus, 20 articles met eligibility criteria and were included in the review.See Figure 1 for a PRISMA ow chart of the article search and selection process.

Measurement of IWS
Measurement of IWS was highly consistent across included studies, with 8 studies (23,28,30,33,38,39,41,44) using the Weight Bias Internalization Scale (WBIS) (12); 9 studies (25,28,34,35,(38)(39)(40)42,43) using the Weight Self-Stigma Questionnaire (WSSQ) (45); and 6 studies (27,29,31,32,36,37) using the Modi ed Weight Bias Internalization Scale (WBIS-M) (46), a modi ed version of the WBIS for individuals of all body weights.These measures were used to evaluate changes in IWS from baseline to post-intervention and over follow-up periods.The WBIS was developed to assess the degree to which respondents believes that negative stereotypes about individuals with higher weight apply to them and includes items such as: "As an overweight person, I feel that I am just as competent as anyone"; "I am less attractive than most other people because of my weight"; and "I hate myself for being overweight" (12).Some in the WBIS-M were modi ed to be applicable to individuals who do not have higher weight, such as: "Because of my weight, I feel that I am just as competent as anyone" and "I hate myself for my weight" (46).The WSSQ was developed to assess self-devaluation based on weight and fear of enacted weight stigma; it includes items such as: "I'll always go back to being overweight"; "I feel guilty because of my weight problems"; and "People think that I am to blame for my weight problems" (45).
Session attendance was generally high across studies; one study with two arms reported higher attendance and adherence rates in intervention conditions compared to controls (29), whereas another study found lower attendance and engagement in the intervention group relative to control (28).

Discussion
This review synthesized ndings from 20 studies evaluating the feasibility, acceptability, and preliminary e cacy of psychological interventions for IWS and their impact on related health outcomes.Table 2 outlines key terms and ndings.• Interventions using psychological approaches to promote body acceptance, self-compassion, and reject weight stigma demonstrate feasibility and acceptability.
• Data on whether interventions produced greater reductions than control conditions were mixed.
• Additional research using rigorous study designs (e.g., randomized controlled trials) is needed to further evaluate the e cacy of interventions for IWS.
Of the 20 included studies, 65% reported on feasibility, acceptability, and engagement metrics.Most of these studies demonstrated high feasibility, acceptability, and session attendance.Most studies (n = 16) reported signi cant reductions in IWS from baseline to post-intervention and at follow-up assessments.These reductions were observed across numerous intervention types including behavioral weight loss, body gratitude journaling, physical activity promotion, and weight stigma interventions and across modalities including group formats, guided self-help, and online courses.However, data on whether interventions produced greater reductions than control conditions were mixed.Six studies with control conditions showed greater decreases in IWS in the intervention groups compared to controls, whereas 5 found no differences (i.e., the intervention and control groups experienced equal reductions in IWS).This nding may suggest that some interventions are more e cacious at addressing IWS, or that common factors within the interventions and control conditions (e.g., supportive group treatments) were helpful for reducing IWS.Of note, both the WBIS and WSSQ were represented in studies which did and did not report differences between conditions.However, Pearl et al. (38,39) found that changes in WBIS scores did not differ between intervention (behavioral weight loss plus a cognitive-behavioral intervention for IWS) and active control (behavioral weight loss alone) groups, whereas decreases in WSSQ scores were greater in the intervention condition.This nding may suggest that there are meaningful differences in measurement of IWS constructs between the WBIS and WSSQ.For example, although both measures assess self-devaluation based on weight, the WSSQ also captures perceived weight stigma enacted by others (e.g., "People discriminate against me because I've had weight problems") (45); this construct may have been more sensitive to intervention effects in the above studies.Another possible explanation for the discrepancy in ndings is that participants in these two studies were selected based on a WBIS cut-off score (but not a WSSQ cut-off score), which may have resulted in less variability in WBIS scores in the sample.
In addition to reductions in IWS, several included studies reported improvements in a range of psychosocial and physiological outcomes, such as increased physical activity, improved blood pressure, and HDL cholesterol levels.Studies that included IWS interventions in combination with lifestyle modi cation focused on weight management were particularly effective in producing weight loss.These ndings highlight the potential for interventions to signi cantly improve both IWS's mental health correlates and associated negative clinical outcomes.While lifestyle modi cation programs with added IWS intervention components did not produce greater weight losses than lifestyle modi cation alone (38, 39), a nding which does not support the hypothesis that addressing IWS may further improve weight loss (25), neither do IWS interventions negatively impact weight outcomes.IWS interventions may be an important addition to lifestyle modi cation programs to prevent the emergence of, or reduce existing,

IWS in patients.
This review served as an important rst step to demonstrate that psychological interventions can produce meaningful reductions in IWS, a critical direction given the harmful effects of IWS on physical health, mental health, and healthcare services use (15,17).Strengths of the review included the rigorous methodological approach used for study selection, which included the involvement of a medical librarian and screening of over 150 studies.Limitations included that many included studies had small, homogeneous samples.Further research in larger, more diverse samples is needed.Further, the variability in types of interventions evaluated (e.g., lifestyle modi cation, body appreciation interventions) and psychological approaches used (e.g., self-compassion, mindfulness and acceptance) preclude us from being able to identify intervention components or approaches that effectively reduce IWS.
Future research is needed to rigorously evaluate interventions using RCTs and examine the mechanisms through which these interventions impact IWS and related health outcomes.Conclusions This review synthesized the existing literature on psychological interventions for the reduction of IWS.Findings indicated that existing interventions are feasible, acceptable, and may provide meaningful improvements in IWS and associated health outcomes, highlighting the potential for psychological interventions to promote improved health and wellbeing in individuals with IWS.43.Palmeira L, Cunha M, Pinto-Gouveia J. Processes of change in quality of life, weight self-stigma, body mass index and emotional eating after an acceptance-, mindfulness-and compassion-based group intervention (Kg-Free) for women with overweight and obesity.J Health Psychol.2019;24(8):1056-69.44.Forbes YN, Mo tt RL, Van Bokkel M, Donovan CL.Unburdening the Weight of Stigma: Findings From a Compassion-Focused Group Program for Women With Overweight and Obesity.J Cogn Psychother.2020;34(4):336-57.45.Lillis J, Luoma JB, Levin ME, Hayes SC.Measuring Weight Self-stigma: The Weight Self-stigma Questionnaire.Obesity.2010;18(5):971-6.4 .Pearl RL, Puhl RM.Measuring internalized weight attitudes across body weight categories: validation of the modi ed weight bias internalization scale.Body image.2014;11(1):89-92.

Figures
Figures included interventions speci cally designed to target IWS, including adjunctive IWS interventions integrated within other interventions, as well as interventions that did not explicitly target IWS but included it as an outcome.MethodsThis systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (26).

Table 2
Key terms and ndings.

Table Table 1
is available in the Supplementary Files section.