Surgery is the cornerstone of treatment for patients with oesophageal or gastric cancer, but while surgical removal of the tumour (oesophagectomy or gastrectomy) may offer the best chance of cure, these are major operations associated with specific long term complications. Weight loss and poor nutrition are relatively common problems among patients who attain long-term cancer remission and cure after surgery. The mechanisms underlying these problems are not well understood and therefore treatment options are limited.

The investigators research has demonstrated increased levels of chemical messengers (gut hormones) released from the gastrointestinal tract after meals in patients who have previously undergone upper gastrointestinal surgery. These chemical messengers play a role in signalling the feeling of fullness during and after a meal (satiety). Understanding the mechanisms involved in increased gut hormone secretion after these operations may allow us to use certain medications to block gut hormone release and hence reduce satiety allowing patients to eat more, regain weight and prevent nutritional complications after surgery.

Exaggerated post-prandial satiety gut hormone responses following oesophagectomy have, however, only been established cross-sectionally and therefore the time course for development of increased gut hormone secretion is unknown. Data collected from this study will provide important information about optimal timing of therapeutic intervention in this patient group, while offering mechanistic insights with regard to the pathophysiologic process underlying post-operative early satiety.

Inclusion Criteria:

• Patients scheduled to undergo two-stage, three-stage or transhiatal oesophagectomy with gastric conduit reconstruction OR total gastrectomy with Roux-en-Y reconstruction

Exclusion Criteria:

1. Significant and persistent chemoradiotherapy complication
2. Other previous upper gastrointestinal surgery
3. Unwell or unable to eat
4. Other disease or medications which may affect satiety gut hormone responses
5. Active and significant psychiatric illness including substance misuse
6. Cognitive or communication issues or any factors affecting capacity to consent to participation
7. History of significant food allergy, certain dietary restrictions
8. Confirmed or suspected residual or recurrent disease after surgery, synchronous or metachronous malignancy
9. Significant surgical complication, aspiration risk or deterioration in performance