Tsai J.F.Rudeejaroonrung K.Chaimano S.Efendi F.Lin C.Y.Lee C.T.Ng A.K.Paratthakonkun C.Strong C.Tsai M.C.Mahidol University2026-02-062026-02-062026-01-01Journal of Psychiatric Research Vol.192 (2026) , 10-1900223956https://repository.li.mahidol.ac.th/handle/123456789/114331Disordered eating and exercise behaviors may co-occur with muscle dysmorphia. This study investigates potential psychological mediators (psychological distress, weight self-stigma, drive for muscularity, drive for leanness) of the relationships between muscle dysmorphia and exercise addiction and muscularity-oriented eating in young Taiwanese individuals. We also examined whether these mediating effects differed by sex and sexual orientation. A cross-sectional sample of 1500 young adults (M<inf>age</inf> = 22.3 years, 38.3 % male) participated in an anonymous online survey. We performed mediation analyses using AMOS to investigate the indirect effects of potential psychological mediators and multi-group analyses to examine the variation between males and females and between heterosexual and non-heterosexual individuals. We found that weight self-stigma, drive for muscularity, and drive for leanness were significant mediators, and these effects were invariant across sex and sexual orientation. Psychological distress, weight self-stigma, drive for muscularity, and drive for leanness mediated the relationship between muscle dysmorphia and muscularity-oriented eating. Males were more likely to report muscularity-oriented eating influenced by weight self-stigma and drive for leanness, and drive for leanness was more likely to facilitate heterosexual participants toward muscularity-oriented eating than non-heterosexual subjects. Successful interventions for disordered eating and exercise require an understanding of the underlying psychological and behavioral drivers.NeuroscienceMedicineArticleSCOPUS10.1016/j.jpsychires.2025.10.0262-s2.0-1050199592221879137941130169