Randomized comparative study to examine the effect of early exercise and parenteral nutrition therapy intervention on lean body mass loss after gastrectomy

INTERVENTION: Amino acid‐containing infusion is administered from 1st to 5th day after surgery. Rehabilitation is carried out every day in line with behavior objective from the next day after surgery. Maintenance infusion is administered from 1st to 5th day after surgery. Rehabilitation is carried out every day in line with behavior objective from the next day after surgery. CONDITION: Gastric Cancer PRIMARY OUTCOME: Percentage of lean body mass loss on 7 days after gastrectomy. SECONDARY OUTCOME: 1) Percentage of lean body mass loss on 1 month and 3 months after gastrectomy; 2) Changes of body weight, body composition (lean body mass / skeletal muscle mass / muscle mass / fat mass), and skeletal muscle index up to 1 year after surgery; 3) Changes in walking speed, grip strength, and 5 times chair standing test up to 1 year after surgery; 4) Incidence of postoperative complications; 5) Postoperative inflammatory condition; 6) Changes in nutrition index up to 1 year after surgery; 7) Energy intake up to 1 year after surgery; 8) Postoperative exercise compliance; 9) Postoperative chemotherapy compliance INCLUSION CRITERIA: