Despite recent reports, the effectiveness of postoperative oral nutritional supplementation (ONS) on body weight loss and malnutrition after gastrectomy remains controversial. We aimed to elucidate the effectiveness of ONS especially in octogenarian patients undergoing oncological gastrectomy.

A total of 286 consecutive patients who underwent gastrectomy for gastric cancer were eligible. Postoperative body weight loss, malnutrition, and sarcopenia were compared between patients with and without postoperative ONS among octogenarian patients aged ≥ 80 years and non-octogenarian patients aged < 80 years.

In this study, 36 (62.1%) octogenarian and 121 (53.1%) non-octogenarian patients continued postoperative ONS for three months. The clinicopathologic characteristics were not different between the ONS (−) and ONS (+) groups among the octogenarian and non-octogenarian patients. The changes in body weight and serum albumin levels at postoperative 1 year were different between the ONS (−) and ONS (+) groups (P = 0.03 and P = 0.04, respectively) among the octogenarian patients, but not between the two groups among the non-octogenarian patients (P = 0.99 and P = 0.29, respectively). Also, the decline in psoas muscle mass index at postoperative 6 months and 1 year was significantly lower in the ONS (+) group than in the ONS (−) group (P < 0.01 and P < 0.01, respectively). In addition, similar results were found in octogenarian patients who underwent distal gastrectomy.

Postoperative ONS could prevent body weight loss, malnutrition, and sarcopenia especially in octogenarian patients who underwent gastrectomy for gastric cancer.