Gastric bypass

Bariatric surgeons at The London Clinic are experienced in the Roux-en-Y gastric bypass (RNY). This is by far the most common of the many variations of gastric bypass operations that are performed in the world today.


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Weight management

What is it for?

To help treat obesity

Treatment overview

Roux-en-Y gastric bypass is a more extensive and complex procedure than a sleeve gastrectomy. It is suitable for people with a BMI of 50 or less, as it is not safe to attempt in more obese patients.

A gastric bypass separates off a major part of the stomach, creating a small stomach pouch that reduces the amount of food you can eat.

The bypass part of the surgery then diverts the path of food after it leaves the stomach. Normally food leaves the stomach and passes through sections of small intestine that are around 6 metres long.

A gastric bypass creates a new opening at the bottom of the stomach pouch, which is connected to a point further down the small intestine.

A gastric bypass therefore leads to weight loss in two ways:

  1. The small stomach pouch reduces the amount of food you can eat: this is the most important component.
  2. The bypass of some of the small intestine prevents you absorbing some of the calories and other nutrients from your food.
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What does a gastric bypass involve?

The procedure can usually be performed by laparoscopic (keyhole) surgery and takes approximately one hour. It is classed as major surgery and is not straightforward to reverse. Most patients stay two nights in hospital.

You need to be prepared to work hard after your surgery to make sure that you eat the right balance of nutrients. Your ability to digest food is impaired after surgery, and you need to make sure you do not develop malnutrition.

Your eating habits will change as they do after a sleeve gastrectomy.

What results can I expect?

Weight loss following a gastric bypass is generally 70% of excess weight at two years. This is greater than that achieved with a gastric band or sleeve gastrectomy alone.

If you have type 2 diabetes this can go into remission. This can happen within a day to up to six weeks following the surgery in most patients because insulin resistance is lowered.

Sustained weight loss and benefits to health then depend on your commitment to maintaining a healthy diet and taking nutritional supplements for the rest of your life.

What problems might I experience with a gastric bypass?

Major complications include:

  • Leakage at the junction between the stomach and the small intestine. General statistics show this occurs in one in 200 gastric bypass operations done in the UK though it is very rare with our experienced surgeons.
  • Formation of peptic ulcers at these joins. Generally this affects one in 100 patients. Each patient should be monitored to detect and treat ulcers promptly.
  • Internal hernias, which are extremely rare but can be serious.
  • Dumping syndrome, which is very important to patients who have a sweet tooth. If you have a gastric bypass and you eat high-sugar food, the sugar rush directly into the lower part of the small intestine makes you feel light-headed and queasy. This happens because you produce a spike of insulin to deal with the sugar. The feeling that you get with dumping syndrome is so unpleasant that your brain is re-programmed to avoid sweet foods.

Why choose The London Clinic

Excellence in one place

We operate as teams of experts with world-class resources dedicated to maintaining the highest standards of medical care. You are surrounded by the latest treatments and advice with everything you need to get back to your best health.

Personal care, every time

Exceptional patient care is a way of life for us. Our nurses, clinicians and support teams are dedicated to the care of a very small number of patients, so have more time for you. They’ll be with you every step of the way, tailoring your care around you and giving the peace-of-mind that comes with knowing you’re in the best hands.

Effortlessly simple

We work together as one to guide you through each step of your experience, with complexities unravelled and answers readily to hand. Your personal treatment plan will be laid out for you, with all the details taken care of so you can focus on you.

What's included in your package?

Choosing The London Clinic means your treatment plan will be laid out for you, with all the details taken care of so you can focus on you.


Your treatment package will include:

  • Enhanced pre-admission assessment
  • Your treatment with our complete care team at your fingertips
  • Personalised aftercare and follow-up

We want you to be in control of your health. That’s why we also offer optional services such as comprehensive recovery packages and extra touches for you to choose from during your stay with us.

How to pay

  • You can use private medical insurance (PMI) to access this treatment. We work with all major PMI providers in the UK and many internationally
  • You can pay for yourself (self-pay)
  • If you’re paying for yourself, we have finance options available with Chrysalis

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