BACKGROUND: Patients with Crohn's disease (CD) often develop malnutrition due to disease activity. We aimed to assess the effect of two different enteral supplements of Impact(R) Powder (IP; Novartis, Switzerland) on leptin levels and nutritional status in active CD patients during prednisolone treatment and tapering. METHODS: Thirty-one CD patients were randomized to IP Extra (group 1) or IP Standard (group 2). Leptin levels, nutritional, clinical and biochemical markers were studied at inclusion, after 5 and after 9 weeks of the study. RESULTS: Leptin levels, body mass index (BMI) and total cholesterol increased significantly within both groups at week 5 compared to inclusion. Leptin levels correlated with BMI in both groups at inclusion and in group 2 at week 9. In group 1, triglyceride levels remained unchanged, while levels in group 2 increased significantly at week 5 compared to inclusion. Clinical and biochemical markers improved during the study compared to inclusion. CONCLUSIONS: Increased leptin levels during the study progress were transient, decreasing due to prednisolone withdrawal at the end of the study. Both formulas used as adjuvant therapy to prednisolone treatment were able to improve nutritional status in CD patients.