European data suggests that over 30% of gastric cancer (GC) patients are diagnosed with sarcopenia before surgery, while unintentional weight loss occurs in approximately 30% of patients following gastrectomy. Preoperative sarcopenia significantly increases the risk of major postoperative complications, and preoperative body weight loss remains a superior predictor of outcome and an independent prognostic factor for overall survival (OS) in patients with GC. A standardized approach of nutritional risk screening of GC patients is yet to be established. Therefore, the MOONRISE study aims to prospectively analyze the changes in nutritional status and body composition at each stage of multimodal treatment among GC patients from five Western expert centers. Specifically, we seek to assess the association between nutritional status and body composition on tumor response following neoadjuvant chemotherapy (NAC). Secondary outcomes of the study are treatment toxicity, postoperative complications, quality of life (QoL), and OS. Patients with locally advanced gastric adenocarcinoma scheduled for multimodal treatment will be included in the study. Four consecutive nutritional status assessments will be performed throughout the treatment. The following study was registered in ClinicalTrials.gov (Identifier: NCT05723718) and will be conducted in accordance with the STROBE statement. The anticipated duration of the study is 12–24 months, depending on the recruitment status. Results of this study will reveal whether nutritional status and body composition assessment based on BIA will become a validated and objective tool to support clinical decisions in GC patients undergoing multimodal treatment.