The primary objectives of this study is o evaluate the safety of a leucine-restricted diet in patients with gastric cancer and determine the impact of a leucine-restricted diet on serum amino acid concentrations in patients with gastric cancer.Besides,we can assess changes in the immune microenvironment of gastric cancer patients following administration of a leucine-restricted diet and observe alterations in body composition of gastric cancer patients after the application of a leucine-restricted diet.

Inclusion Criteria:

• Pathologically confirmed gastric carcinoma requiring preoperative endoscopic localization marking or delineation of the lesion extent.
• Aged between 18 and 70 years, regardless of gender.
• Ability to consume oral or nasogastric tube feeding of a liquid diet.
• Provision of signed informed consent and voluntary participation in this study.
• No evidence of distant metastasis on preoperative imaging studies (e.g., CT, PET-CT), and deemed suitable for surgical resection.
• No concurrent diagnosis of other active malignancies.

Exclusion Criteria:

• Presence of cognitive impairment or psychological disorders that may compromise the understanding of the research content.
• Diagnosis of Type I or Type II Diabetes Mellitus.
• Severe diarrhea, intractable vomiting, severe malabsorption syndromes, paralytic or mechanical intestinal obstruction, or active gastrointestinal bleeding.
• Known allergy to the primary components of the leucine-deficient nutritional formula.
• Concurrent use of other nutritional supplements that may interfere with the trial's efficacy.
• Postoperative pathological diagnosis confirming non-primary gastric cancer.