Gastric bypass surgery

Gastric bypass surgery is an operation that makes your stomach smaller and bypasses a segment of your small intestine.

Reviewed by Mr Ahmed Ahmed, Consultant GI and Bariatric Surgeon

At a glance

What is 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.

The operation is performed using keyhole surgery and normally takes 45-60 minutes.

For more commonly asked questions around gastric bypass surgery, visit our blog.

You are likely to be recommended gastric bypass surgery if you have tried and failed to lose weight and meet the following requirements:

  • Your BMI is above 35
  • You have BMI of 30 and above (or above 27 if Asian) and have type 2 diabetes

You must also be willing to commit to long-term dietary and lifestyle changes, which will be monitored at follow-up appointments.

Gastric bypass surgery is not recommended for women who are planning to become pregnant within 12 months of the procedure.

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.

You’ll normally be able to go home one to two days after the operation. You can resume walking as soon as possible and return to work and normal activities within a week of surgery.  You can travel a week after surgery.

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.

Following a gastric bypass, you may experience some bruising, swelling and tenderness around the operation site.

When you begin eating again following surgery, you may feel sick or even vomit. This is because your stomach needs to adjust to consuming smaller amounts of food.

Gastric bypass also carries a risk of more serious complications, including:

  • Wound infection
  • Gastric leakage (anastomotic leak) leading to potential peritonitis
  • Internal hernia leading to bowel blockage
  • Stomach ulcer
  • Malnutrition

Gastric bypass surgery is an operation that comes with lifelong commitments – it isn’t an easy route to weight loss.

Before deciding whether to have surgery, patients should consider the following:

  • Dietary and lifestyle changes: For your surgery to be successful, you will need to be committed to following a healthy, balanced diet and exercising regularly.
  • Follow-up appointments: You will need to be able to attend scheduled follow-up appointments after

There are several different types of bariatric treatment, both surgical and non-surgical. If you would prefer a non-surgical approach, we offer treatments including weight loss injections, gastric balloons and endoscopic sleeve gastroplasty (ESG).

Find out more about our bariatric treatments >

Lifestyle changes after gastric bypass surgery

For gastric bypass surgery to be successful, patients must be able to commit to the necessary dietary and lifestyle changes. In the days and weeks following your surgery, you will have to adjust your eating habits as your stomach readjusts to its new, smaller size.

You won’t be able to return to regular, solid foods immediately after surgery – this is because your stomach needs time to adjust. Instead, you’ll asked to follow a schedule roughly similar to the below.

First few days – water and liquids (such as soups, yoghurt and milk)
First four weeks – puréed foods (such as scrambled eggs or mashed potato)
Weeks four to eight – soft foods (such as fish, pasta, rice and minced meats)
Week eight onwards – a phased return to a regular, balanced diet

You will also be advised to eat slowly and avoid heavier foods, such as white bread or red meat. You will also need to take nutritional supplements, such as a good multivitamin, daily.

Your consultant will advise you on exercise following gastric bypass surgery. Generally, you will be asked to do low-impact exercises for a short amount of time, like walking or swimming.

Eventually, you will have a phased return to more high-impact exercises, like aerobic exercises, running and weight training. As well as helping you to lose weight, regular exercise also helps improve your overall health and wellbeing.

You will require regular follow-up appointments after surgery. This is to ensure that you are losing weight and maintaining good health.

You will also need to have yearly blood tests to ensure your body is getting enough nutrients.

Why choose us for gastric bypass surgery?

Private bariatric surgeons in London

Led by Mr Ahmed Ahmed, our bariatric consultants are experts in their field and have a wealth of surgical experience.

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We welcome both self-paying and insured patients.

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