Based on existing literature, we posit that a leucine-restricted diet is safe and well-tolerated in patients with advanced gastric cancer receiving combined chemotherapy and immunotherapy. Patients adhering to this dietary regimen exhibit a significant reduction in serum leucine concentrations, with no notable impact on the serum levels of other amino acids. Furthermore, leucine restriction promotes the activation of immune cells within the tumor microenvironment. When applied in conjunction with chemotherapy and immunotherapy for advanced gastric cancer, this approach demonstrates synergistic anti-tumor efficacy. It is expected to enhance tumor response rates , improve the 1-year survival rate, prolong overall survival (OS), and ultimately optimize patient prognosis.