Patients with advanced gastric adenocarcinoma are at high risk of malnutrition. Some patients benefit from total gastrectomy associated with hyperthermic intraperitoneal chemotherapy (HIPEC) with or without cytoreduction surgery (CR) as a curative strategy. The aim of this study was to describe pre- and post-operative nutritional assessments and their impact on survival in these patients. All patients with advanced gastric adenocarcinoma treated with gastrectomy and HIPEC with or without CR at Lyon University Hospital were retrospectively included from April 2012 to August 2017. Carcinologic data, history of weight, anthropometric measures, nutritional biological markers and CT-scan body composition were collected. 54 patients were included. Malnutrition affected 48.1% before and 64.8% after surgery, and severe malnutrition respectively 11.1% and 20.3%. Pre-operative sarcopenia diagnosed by CT scan was found in 40.7% of the patients while 81.1% of the sarcopenic patients had a normal or high body mass index. A loss of ⩾ 20% of usual weight on discharge was a pejorative factor of survival at 3 years of follow-up (p = 0.0470). Only 14.8% of the patients continued artificial nutrition following discharge but artificial nutrition was resumed in 30.4% of the patients within 4 months after discharge owing to weight loss. Patients with advanced gastric adenocarcinoma undergoing gastrectomy and HIPEC with or without CR are at high risk of malnutrition. Post-operative weight loss has a pejorative impact on outcome. These patients should be systematically screened for malnutrition with early interventionist nutritional care and close nutritional follow-up.