Background <p>Weight stigma among health professions students may negatively influence patient communication, clinical decision-making, and healthcare engagement for individuals with obesity. Educational approaches have demonstrated limited impact on implicit attitudes and affective competencies central to patient-centered care. This randomized controlled trial evaluated whether an exercise-based obesity simulation reduces weight bias and improves professional learning outcomes in health professions students.</p> Methods <p>In a three-arm randomized controlled trial, 107 undergraduate health professions students were randomly allocated to one of three conditions: control (non-exercise session), exercise-only, or exercise with an obesity simulation suit. The intervention consisted of a single 30-min supervised treadmill session. Outcomes were assessed at baseline, 1-week, and 8-week follow-up and included implicit weight bias, explicit weight bias, beliefs about obesity, clinical decision-making using patient-centered vignettes, behavioral intentions toward future patients, and structured reflective learning. Group x time effects were examined using repeated-measures analysis of variance. Multiple regression analyses explored whether affective responses during the intervention were associated with changes in learning outcomes at eight weeks.</p> Results <p>Significant group x time interactions were observed for implicit weight bias, explicit bias related to controllability beliefs, clinical decision-making, and behavioral intentions (all <i>p</i> &lt; 0.05). Compared with control and exercise-only groups, participants in the simulation condition demonstrated reductions in implicit and explicit bias and increases in patient-centered decision-making at 1-week, with effects sustained at 8-week follow-up. Behavioral intentions toward weight-inclusive care also improved in the simulation group at both follow-up time points. Reflective learning scores were higher in the simulation group at 1-week. Lower positive affect during the simulation was associated with greater improvements in several learning outcomes.</p> Conclusions <p>A brief exercise-based obesity simulation reduced weight bias and improved clinical reasoning and professional intentions among health professions undergraduate students, with effects persisting for eight weeks. This single-session experiential intervention may offer a feasible and scalable strategy for integrating bias reduction and patient-centered competencies into health professions education.</p> Trial registration <p>ClinicalTrials.gov NCT07430891. Registered February 23, 2026. Retrospectively registered.</p>