Objective:
Eating disorders (EDs) in men are underdiagnosed and undertreated, partly due to stigma hindering help-seeking. This randomized waitlist-controlled study tested the efficacy of the iSMEsH online anti-stigma intervention targeting German general practitioners (GPs) and medical students. The program aimed to reduce stigmatizing attitudes toward men with EDs and improve knowledge and self-efficacy in managing ED symptoms.

Method:
A total of 292 participants (130 GPs, 162 medical students) were randomly assigned to immediate intervention or waitlist control. The intervention consisted of six video-based, on-demand modules co-developed with men who have lived experience of an ED, combining education and contact-based strategies. Outcomes included cognitive stigma (knowledge), affective stigma (biased attitudes), and behavioral stigma (treatment self-efficacy), assessed at three timepoints.

Results:
The iSMEsH anti-stigma intervention significantly increased knowledge of male-specific ED presentations and enhanced treatment self-efficacy in both GP and medical student populations. Effects on affective stigma were less consistent.

Discussion:
Findings support the efficacy of the iSMEsH anti-stigma intervention in improving knowledge and treatment self-efficacy regarding EDs in men among healthcare professionals. Effects on affective stigma were limited and may require longer follow-up periods to be comprehensively captured. The intervention shows promise as a scalable tool to reduce stigma and improve care for men with EDs.

Trial Registration:
On July 1, 2024 (#181,415; https://aspredicted.org/tzds-h5yq.pdf) and a study protocol is published under Lehe et al. (2025)