The Effects of Preoperative and Postoperative Oral Nutritional Supplements in Malnourished Post-gastrectomy Patients

Inclusion Criteria: * Patients older than 20 years * Patients who undergo distal, total, proximal, or pylorus-preserving gastrectomy * Patients who are assessed as moderate or severe malnourished according to PG-SGA or patients with BMI lower than 18.5 kg/m2 * Patients who can take oral meals * Patients who agree on the informed consent Exclusion Criteria: * Emergent operation * Patients who received preoperative chemotherapy or radiation therapy within 6 months * Pregnant patients * Patients who cannot consume the Ensure powder * Patients who enrolled another clinical trials