This prospective observational cohort study examines the energy requirements and nutritional care of patients undergoing total or partial pancreatectomy for pancreatic tumors. Patients undergoing pancreatectomy face major metabolic stress, a high burden of preoperative malnutrition, and frequent exocrine or endocrine insufficiency, yet procedure-specific nutritional guidance is limited. The study measures resting energy expenditure (REE) directly by indirect calorimetry during the early postoperative period and compares it with widely used predictive equations (Harris-Benedict, Schofield) and simplified weight-based targets (25 and 30 kcal/kg) to determine how accurately clinicians can estimate energy needs when calorimetry is unavailable. In the same patients, the study records the route of postoperative nutrition (enteral, parenteral, or combined), energy and protein intake relative to requirements, and diet-related symptoms, and follows postoperative complications, hospital readmission, mortality, and changes in body weight and body mass index through 3-6 months after surgery. By capturing measured energy expenditure and nutritional delivery in one cohort, the study aims to clarify whether adequacy of energy and protein intake, feeding route, or both influence recovery, and to provide primary data for developing individualized nutritional support protocols in this high-risk surgical population.