Figure 2 depicts the selection flow as per PRISMA guidelines. Across the databases, after duplicates were removed, 266 articles were identified. Six additional articles were identified during manual screening of reference lists. Following quality assessment, 19 studies remained for data extraction.

PRISMA flowchart of article screening and selection process

Of the 19 studies included, 21% (n = 4) were prospective studies and 79% (n = 15) were cross-sectional. Fifteen relied on retrospective data analyses. Ten studies were included from Eurocentric countries (Germany [21, 32,33,34], Australia [24], USA [35,36,37,38], Canada [32]), six from Asian (China [26, 39], Hong-Kong [26], Korea [40]) and three from Middle Eastern countries (Iran [41, 42], UAE [43]). A majority of studies (68.4%) were published between 2019 and 2021. The earliest study included was published in 2012.

Only six studies provided information on the ethnicity of participants. A majority (69.83%) of identified ethnicities were white. Only, 14.53% were identified as black, 10.76% as Hispanic or Latino, 8.29% as Asian, and 5.80% were identified and classified as other by the study authors. Of the participants, 61.45% were female, and 38.55% were male, with four studies exclusively investigating a female population. Three studies [21, 32, 33] investigated the role that sex played on IWB scores and found females to have higher IWB scores, whilst two found no difference [35, 38]. Lastly, the ages of participants ranged from 5 to 25 years. Three studies involved dyads of one parent and child [39].

To assess IWB, studies predominantly used the Weight Bias Internalization Scale (WBIS; n = 16, 84.21%) or a modified version and the Weight Self-Stigma Questionnaire (WSSQ; n = 5, 26.32%). One study that utilised the Weight- and Body-Related Shame and Guilt Scale (WEB-SQ) was included in this review due to it explicitly stating that it was used as a measure of IWB. Seven of the 19 studies modified the Weight Bias Internalization Scale: four used a modified WBIS (WBIS-M), two a child WBIS (WBIS-C), one a WBIS tool for youth (WBIS-Y) [26, 32, 44], Table 1.

Table 1 summarises all included studies on IWB and outcomes in children and youth. All studies included at least one validated measure of a biopsychosocial outcome, with high variability in the types of tools used.

All nineteen studies found positive associations between higher levels of IWB and at least one negative psychological outcome [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28, 31, 34,35,36, 38,39,40]. The findings are summarised in Fig. 3 which demonstrates the associations between IWB and psychological distress, eating disorder symptomology, self-esteem, and quality of life as IWB scores increased.

Heat map indicating the relationships reported in included studies of IWB. Arrows indicate the direction of relationship with IWB as scores increase. Abbreviations: BMI Body Mass Index, IWB Internalised weight bias, LoC Locus of control. Legend: Colour scale indicates the number of studies (cited by reference number) reporting the same direction of relationship

Positive associations were seen between prevalence of eating disorder symptomology (binge eating, eating to cope, eating restriction, bulimia, oral control, restrained eating, uncontrolled eating, emotional eating), and pathopsychological (emotional problems, depression, anxiety, psychological distress) as IWB scores increased.

IWB was significantly and positively associated with elevated levels of psychopathology and negative psychosocial outcomes [33, 36, 41, 45] across sex and weight groups [33, 41]. IWB mediated the relationship between elevated BMI and quality of life [39], and psychosocial problems [21, 33, 48], with IWB shown to be more important than weight status in explaining psychological functioning [33] via cross-sectional studies. Five studies found IWB significantly and negatively correlated with health-related quality of life [21, 26, 43, 44].

Fourteen studies investigated associations between BMI and IWB. There was heterogeneity in the data for how BMI was measured. Six articles supplied a mean and standard deviation, whilst six recorded the percentage of weight categories (e.g., ‘underweight’, ‘overweight’), and seven reported both. Fifteen (78.95%) studies relied on self-reported data for weight. Six articles only investigated OW or children and youth with a BMI ≥ 30 kg/m2 [21, 36, 41, 42, 45, 46]. Two of the nine studies that explored the weight spectrum had 'normal'/'underweight' participants as a minority, with four of these studies combining the ‘underweight’ and ‘normal’ weight groups [35, 44, 46, 47]. Nine articles found a positive association between IWB and BMI [21, 24, 32,33,34,35,36, 38, 46]. ‘Overweight’ compared to ‘non-overweight’ groups showed higher levels of IWB [24, 36, 39, 44], eating disorder symptomology [24], and decreased quality of life [36, 44], with IWB demonstrating a mediational relationship between physical weight and quality of life [39], Fig. 4.

The suggested mediational relationships between IWB and biopsychosocial outcomes. A Increased BMI and decreased physical [42], weight-related [49], health-related [39], and psychosocial QoL[42], increased BMI and increased psychopathology [42] and emotional problems [33] and increased BMI and decrease physical activity levels [47]. B Increased weight teasing and increased eating symptomology [24, 33] and emotional problems [33]. C Decreased physical activity and decreased health related QoL

Two studies [26, 47] investigated the association between IWB and physical activity engagement, finding a statistically significant negative correlation, with IWB scores being lower in active groups when compared to non-active groups.

Ten studies investigated social outcomes. Five studies [36, 38, 40, 44] found a positive association between IWB and negative social characteristics in individuals (e.g. conduct issues, attachment to teachers, avoidance behaviours, maladaptive behaviours). One study [32] found that higher IWB scores and lower SES were positively associated. Lastly, eight studies found experiences of experienced weight stigma to have a strong positive association with IWB [24, 32, 33, 37,