Radical gastrectomy has been known as the most effective treatment of curable gastric cancer.However, there is a high risk of malnutrition and weight loss after a gastrectomy which may be attributed to inadequate oral consumption, malabsorption and loss of the reservoir function of the stomach.Weight loss has been regarded as an independent risk factor for postoperative mortality and morbidity and It is also closely associated with a quality of life after surgery. No specific surgical technique has been proved to be effective in reducing postoperative weight loss and it seems like that dietary education and consultation is the best way to minimize weight loss in gastrectomy patients in clinical setting. In this regard, the investigators performed a retrospective pilot study to identify the effect of routinely performed (simplified) dietary education on nutritional status after gastrectomy, but it revealed that the effect of simplified dietary education on weight loss was not clear and the result implies that more intensive dietary education may be necessary after gastrectomy. The aim of this randomized controlled trial (RCT) is to elucidate the effect of intensive dietary education on nutritional status after gastrectomy in comparison with simplified dietary education.

Subject 1: subtotal gastrectomy group

subject 2: total gastrectomy group

Objectives:

Primary objective: to evaluate Weight loss difference of simplified dietary education(SE) versus intensive dietary education(IE) for patients after undergoing a gastrectomy

Primary endpoint: Superiority of weight loss difference (%) of IE group between post op 1mo and 12mo

Secondary objectives:

weight loss(%) of each subgroup, nutritional parameters (PG-SGA), Calrorie intake & dietary habits, albumin, hemoglobin, iron panel (TIBC, ferritin), Absolute lymphocyte count(ALC), vit B12, homocysteine, quality of life(QOL) change

1. Nutritional parameters (PG-SGA)
2. the amount of calorie intake (Kcal, protein) & dietary habits
3. Albumin (g/dL)
4. Hemoglobin (g/dL)
5. Iron panel [TIBC (μg/dL), Ferritin (ng/mL)]
6. Absolute lymphocyte count (ALC) (10^3/μL)
7. Vitamin B12 (pg/mL)
8. Homocysteine (μmol/L)
9. Quality of life of the patients in terms of European quality of life questionnaire (EQ-5D)

Inclusion Criteria:

• histologically proven primary gastric adenocarcinoma,

• T1N0, T1N1, T2N0, which are assessed by computed tomography (CT) scan (AJCC 8th classification) and intraoperative surgical staging

• location of primary tumor; antrum, or angle, , lower body or mid body of the stomach

• No evidence of other distant metastasis,

• age ≥ 20 year old, ≤ 75 year old

• no prior or posterior treatment of chemotherapy or radiation therapy against any other malignancies

• adequate organ functions defined as indicated below:

  1. WBC count: 3000/mm3 ~12,000/mm3,
  2. > serum Hemoglobin 8.0 g/dL
  3. > serum Platelet 100 000/mm3,
  4. < serum AST 100 IU/L,
  5. \

double blind