State Urge to be Physically Active as a predictor of rehabilitative weight-related outcome in anorexia nervosa: insights from a ROC-informed model

Background: Restlessness, excessive exercise, and the urge to move are clinically relevant symptoms in anorexia nervosa (AN), often associated with poorer treatment response. This observational study investigated the role of the State Urge to be Physically Active (SUPA) in predicting outcomes of a nutritional rehabilitation program, focusing on weight gain and psychological improvement. Methods: We analysed data from 96 inpatients diagnosed with AN (AN-restricting = 66, AN-binge-purging = 26, and AN-atypical = 4), hospitalized in a specialised eating disorders rehabilitation unit (2024–2025). Assessments included psychological measures, weight trends, SUPA, and psychopharmacological treatment. Results: SUPA levels were established using ROC analysis to identify a cut-off (6.96) for predicting for predicting poor outcome (AUC = 0.552; sensitivity = 81.4%, specificity = 37.5%). ANOVA-RM revealed a significant reduction in SUPA from admission to discharge (F = 7.70, p = .007), independent of pharmacological treatment. However, post-hoc analyses suggest greater improvement in the medicated group (t = –3.08, p = .016). No baseline differences in SUPA were observed across AN subtypes. Correlation analyses showed that SUPA scores significantly correlated with core eating disorder-related psychopathology (all Ps < .001). In a general linear model, higher SUPA at admission significantly predicted poorer weight-related outcomes (p = .044), independently of age, illness duration, and medication use. Conclusion: SUPA levels at admission, based on a ROC-informed threshold, may be a meaningful predictor of weight-related outcomes. Targeted interventions may enhance treatment response and support its integration into individualized care strategies for AN.