Weight bias internalization and risk of disordered eating and unhealthy weight control behaviors in Spanish adolescents: a two-year longitudinal study

Abstract Background Weight bias internalization (WBI) occurs when individuals adopt negative weight-based stereotypes, engaging in self-blame and self-devaluation, and has been linked to adverse outcomes in adolescence. Evidence, mostly cross-sectional, shows associations with body dissatisfaction and disordered eating. Prospective research during adolescence, a critical period for body image and eating pathology, remains scarce, particularly in Mediterranean samples. This two-year prospective study examined whether WBI predicts disordered eating attitudes and unhealthy weight control behaviors (UWCB) in Spanish adolescents. Methods A representative sample of adolescents from Terrassa, Spain, selected through random multistage cluster sampling, completed assessments at baseline (T1, 2022; n = 1,016) and follow-up (T2, 2024; n = 551). Overall retention was 54.2% (551/1,016) and reached 81.3% (422/519) among participants who remained in compulsory secondary education. WBI at T1 (WBIS-M scale) was used to predict T2 outcomes: drive for thinness, body dissatisfaction, bulimic symptoms, binge eating severity, and engagement in UWCB. Analyses included multiple regression models (linear, multinomial logistic, and modified Poisson) adjusted for baseline outcomes, measured weight status, and sociodemographics. Results Higher WBI at T1 prospectively predicted greater disordered eating and overall eating disorder risk at T2 (B = 0.7–3.28; p = 0.029 - <0.001), especially in girls. WBI was associated with significantly greater risk of severe binge eating (RRR = 2.45; p = 0.001) and higher likelihood of engaging in UWCB (RR = 1.04; p = 0.017) in girls. UWCB were highly prevalent (42.1%), particularly among girls (55.4%). Conclusions WBI is a longitudinal predictor of disordered eating and UWCB in Spanish adolescents, with stronger effects in girls. Early interventions should target internalized weight stigma to prevent disordered eating.