Article Selection
A total of 161 articles identified 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paper (n = 10), not a full-length manuscript (n = 7), wrong study design (n = 5), wrong outcome measures (n = 7), unpublished manuscript (n = 3), wrong patient population (n = 1), wrong intervention type (n = 1), and not in English (n = 1).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 flow chart of the article search and selection process.
Study Characteristics
Study characteristics for the 20 articles included in this review are presented in Table 1. Included studies were conducted between 2010 and 2023 and were most often conducted in the USA (n = 16) (23,25,27–41), followed by Portugal (n = 2) (42,43), Australia (n = 1) (44), and Canada (n = 1) (37). Study designs included pilot trials (n = 10) (23,27–30,33,34,36,43,44), randomized controlled trials (RCTs) (n= 9) (25,31,35,37–42), and one proof-of-concept trial (32). The most common intervention approaches were acceptance and commitment therapy (n = 5) (34,35,40,42,43), followed by cognitive-behavioral therapy (n = 3) (23,38,39), self-compassion interventions (n = 3) (28,33,44), weight neutral or intuitive eating interventions (n = 2) (29,36), behavioral interventions (n = 2) (25,30), yoga interventions (n = 2) (27,41), one positive psychology and motivational interviewing intervention (32), one journaling intervention (31), and one implicit stereotype retraining intervention (37). Nine studies evaluated lifestyle modification interventions (i.e., interventions targeting dietary or physical activity change or weight management) (25,28,30,32,35,38,39,42,43), 2 of which evaluated the addition of cognitive-behavioral intervention modules targeting IWS to behavioral weight loss treatment (38,39) and one of which evaluated the addition of a mindful self-compassion intervention following behavioral weight loss treatment (28); 8 studies evaluated interventions focused on weight stigma, IWS, or body gratitude (23,31,33,34,37,40,41,44); 2 studies evaluated interventions targeting disordered eating (29,36); and one study evaluated a stress management intervention (27). Intervention duration ranged from 3 weeks (33) to 72 weeks (20-weeks of group treatment followed by 52 weeks of monthly and every-other-month sessions) (39). Formats included group sessions (n = 13) (23,25,27–30,33,35,38,39,42–44); online courses (n = 2) (36,37); telephone-based interventions (n = 1) (32); and an individual writing-based intervention (n = 1) (31).
The sample sizes of included studies ranged from 12 to 162 participants. Most studies (n = 11) recruited mixed gender samples (23,25,27,30,32,34–36,38–40), and 9 studies enrolled only women (28,29,31,33,37,41–44). The mean age of participants spanned from 20.1 (29) to 53.4 years (23). Three studies (29,31,41) recruited college-aged participants. The racial composition of the samples varied; most studies predominantly enrolled White participants, whereas 3 studies (23,29,38) recruited samples that were <50% White. Studies most commonly targeted participants with body mass indexes (BMIs) above or equal to 25 (n = 10) (27,28,30,33–35,41–44), 5 studies targeted participants with BMIs above or equal to 30 (23,25,28,38,39), one study targeted participants with BMIs above or equal to 27.5 (40), and one study targeted participants who self-identified as living with obesity (37). Eight studies specifically targeted participants with heightened IWS (23,28,31,33,34,38–40).
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 (25,28,34,35,38–40,42,43) using the Weight Self-Stigma Questionnaire (WSSQ) (45); and 6 studies (27,29,31,32,36,37) using the Modified Weight Bias Internalization Scale (WBIS-M) (46), a modified 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 modified 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).
Feasibility and Acceptability of Interventions
Of the 20 included studies, 13 reported on feasibility, acceptability, and engagement metrics (23,28,29,32–35,38–42,44). Most studies (n = 8) reported high acceptability ratings, with participants finding the interventions relevant and useful (23,34,35,38–42). Pearl et al. (39) found higher acceptability and greater change attitudes among participants in the intervention group (behavioral weight loss plus a cognitive-behavioral intervention for IWS) relative to the control group (behavioral weight loss alone). 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).
Effects of Psychological Interventions on IWS
The majority of the included studies (n = 16) reported significant reductions in IWS from baseline to post-intervention and at follow-up assessments (23,28–32,34–36,38–44). Among studies with control conditions, 6 studies found greater decreases in IWS in the intervention group relative to controls (23,31,35,38,39,42), whereas 5 found no differences between conditions (28–30,40,41). While both the WBIS and WSSQ measures were represented in studies which did and did not report differences between conditions, Pearl et al.’s studies (38,39) found that changes in WBIS scores did not differ between intervention and active control groups, whereas decreases in WSSQ scores were greater in the intervention condition. Observed decreases in IWS measures were sustained over long-term follow-ups in most studies that detected effects, with follow-up periods ranging from one-week (31) to 72-weeks (39).
Other Psychosocial and Physiological Outcomes
In addition to reductions in IWS, several studies (n = 19) reported improvements in a range of psychosocial outcomes, including internalized shame, self-compassion, disordered eating, intuitive eating, quality of life, body dissatisfaction, and body appreciation, yet the degree to which outcomes improved more in intervention vs. control conditions were mixed (23,25,27–36,38–44).
Physiological outcomes, such as improvements in physical activity, blood pressure, and HDL cholesterol were observed in numerous studies (n = 9); data were mixed regarding whether outcomes improved more in intervention vs. control conditions (25,28,32,35,38–40,42,43). Reductions in weight were common among studies evaluating IWS interventions in combination with lifestyle modification programs (n = 7) (25,28,30,38,39,42,43).