Gastric bypass surgery

An operation to make your stomach smaller and shorten the length of your small intestine.

About gastric bypass surgery

Gastric bypass surgery involves reducing the size of your stomach and bypassing your lower stomach and part of your intestine. This makes you feel fuller and suppresses your appetite, reducing the amount of calories and nutrients that are absorbed.

Your surgeon is likely to recommend gastric bypass surgery if you have tried and failed to lose weight and:

  • your BMI is above 35
  • you have BMI of 30 and above (or >27 if Asian) and have type 2 diabetes

To do this, your surgeon will put a series of staples near the top of your stomach, creating a small pouch (gastric pouch) that then feeds directly into a section of the small intestine.

Anyone who has this surgery must commit to having long-term follow-up appointments to manage lifestyle and nutrition.

How is gastric bypass surgery carried out?

Gastric bypass surgery is done under general anaesthetic so you'll be asleep. It usually takes around one hour.

Gastric bypasses are usually carried out laparoscopically, using small surgical instruments, guided by a telescope with a video camera – all inserted through a series of small cuts in your abdomen.

Your surgeon will use surgical staples to separate the top section of your stomach from the lower part, creating a 'gastric pouch'. They will then cut an opening in the pouch and connect it to a section of the small intestine.

Your surgeon will close the cuts in your abdomen using dissolvable stitches or small metal clips and place a dressing over the area.

A gastric bypass can also be done using robotic surgery. You should discuss this option with your surgeon during a consultation.

What happens after gastric bypass surgery?

You'll normally be able to go home one to two days after the operation.

Long term – along with adopting a healthier lifestyle – you will need regular blood tests once a year to ensure you are getting enough nutrients. You may also need to take some nutritional supplements such as a generic multivitamin and mineral preparation.

"I would like to thank everyone at Cromwell Hospital for the fantastic way you looked after me. I could not fault anyone during the time I spent with you - from the point I arrived in reception, to the catering team and every member of staff throughout the changes of shift during my stay."

Anonymous, Cromwell Hospital patient

Book an appointment today

Our telephone lines are open 8am to 8pm Monday to Friday and 8am to 2pm Saturdays.

Please note - regrettably we are unable to answer specific medical questions or offer medical advice via email or telephone

Published: 31 January 2020 | Review: 31 January 2023

Disclaimer: This information is published by Cromwell Hospital and is based on reputable sources of medical evidence and experience from over 30 years of treating patients. It has been peer reviewed by Cromwell Hospital doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional. If you have any feedback on the content of this patient information document please email or telephone 020 7460 5901.