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Weight Loss Surgery

Gastric Bypass

at Cadogan Clinic, London’s Leading Cosmetic Surgery Specialists. 

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Best Clinic Aesthetics Awards 2024

We were awarded Best Clinic London at the industry-leading 2024 Aesthetics Awards.

CQC ‘Outstanding’ Leadership

Our Leadership is rated ‘Outstanding’ by the independent healthcare regulator in England.

20 Years of Medical Distinction

We’re now entering our third decade at the top of our field, with over 100 of the country’s best consultants under our roof.

96% Customer Excellence Rating

We support 30,000 patient appointments each year, 96% of which were rated 5*.

Medically Reviewed January 2024, by Mr. Bryan Mayou (GMC: 1414396) - founder of the Cadogan Clinic and one of the world's leading plastic surgeons

What is a Gastric Bypass?

A gastric bypass is an invasive surgery designed to help you lose weight if all other methods, such as dieting and exercising, have failed. It is a major surgery.

In a nutshell, gastric bypass surgery involves stapling the top of the stomach to create a small pouch. This pouch is then attached straight to your small intestine, missing out the stomach, hence the name gastric bypass surgery. The idea is that it takes less food to make you feel full up and your body absorbs fewer calories from the food you eat.

People who have had a gastric bypass generally find that the procedure helps them to lose a lot of weight. It is a fast and effective method of weight loss. By losing excessive weight, you cut the risk of serious illness, such as heart disease and cancer, as well as improving mobility and overall physical and mental health. It can also treat existing medical conditions.

Unlike a gastric band or gastric balloon, a gastric bypass is permanent.

A gastric bypass is carried out under a general anaesthetic using keyhole surgery.

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Why do people have it?

The primary goal of gastric bypass surgery is to lose weight and reduce your risk of serious, potentially life-threatening, conditions. These include cancer, heart disease, stroke, high cholesterol, high blood pressure, obstructive sleep apnoea, joint problems and infertility. Losing weight via a gastric bypass can also help to improve existing medical conditions, such as Type 2 diabetes, acid reflux and osteoporosis.

People who are overweight or obese feel self-concious about their weight which triggers anxiety and depression. It also means they are likely to avoid certain social situations. Losing weight via gastric bypass surgery usually results in a marked improvement in a person’s mental health and improves their quality of life.

Who is suitable?

You must be over 18 to have gastric bypass surgery and have a body mass index (BMI) of 40 or more (severely obese) or have a BMI of 35 to 40 and a condition such as high blood pressure which may improve if you lose your excess weight.

The surgeon must deem you fit enough to have a general anaesthetic and to undergo surgery.

Your surgeon must also be satisfied that you are in good mental health ahead of surgery.

Most importantly of all, you must be committed to changing your lifestyle and diet after the operation in order to get the very best results from your gastric bypass.

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The cost of Gastric Bypass

Cadogan Clinic has collaborated with Chrysalis Finance to offer a variety of payment choices for our patients including:
12 months 0% Interest-free - APR
24 - 60 months at 12.9% APR
Flexible Finance

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How does a Gastric Bypass work?

In a gastric bypass, the digestive system is ‘re-plumbed’ so that the food bypasses much of the stomach and instead goes straight into the small intestine.

The surgeon will use surgical staples to create a small pouch at the top of the stomach. The rest of the stomach is untouched. When you eat, the food will go into this pouch. The surgeon will make an opening in the pouch for the small intestine to be attached, so food will travel from the pouch straight into the intestine before continuing its journey through the rest of the digestive tract. The food will no longer travel through the lower part of your stomach or the first part of your bowel.

A gastric bypass works by reducing the amount of food that you are physically able to consume. The operation also alters the hormone levels produced in the gut, making you feel less hungry. By altering these hormone levels, this can also help to improve Type 2 diabetes.

Because of the changes made to the body by gastric bypass surgery, you will need to take supplements for the rest of your life to ensure you get all the vitamins and minerals that you need to stay healthy. You may also need regular vitamin B12 injections and regular blood tests to check you’re getting all the nutrients you need.

What to expect

Below you will find some key information to help you prepare for surgery and make necessary arrangements to ensure you have the support you need and that everything runs smoothly on the day.

The first step for all of our patients is to meet with the surgeon we feel is best placed to perform your procedure for a consultation.

At the consultation you will be able to discuss with your surgeon what your hope to achieve from the procedure, as well as discuss in detail what may or may not be possible.

Finally a comprehensive discussion regarding risks and complications will take place, alongside a discussion regarding the post procedure and recovery phase. Your previous medical history will also be recorded (including previous surgery, medications, allergies etc.) and an assessment of your fitness for surgery.

If your surgeon feels you are a good candidate for surgery, you are then invited to consider whether you would like to proceed for surgery or otherwise following a two week 'cooling off' period.

Within this period you are welcome to come in and discuss your potential surgery with your surgeon as many times as you like.

If you choose to proceed with surgery, the next time you come into the Clinic after your final consultation will be the day of your procedure.

Before admission the following behavioural changes are recommended / required:

  • In the 6 weeks before your procedure we recommend smoking is discontinued as patients who smoke have a higher risk of healing more slowly and complications
  • In the week before your procedure you must cease taking Aspirin or any medication that contains Aspirin
  • In the 6 hours prior to surgery you must not consume food or any drink, other than small sips of clear fluid (e.g. still water, black coffee, black tea) which are allowed up to 2 hours before admission)

Gastric bypass surgery is carried out under a general anaesthetic and is done via minimally invasive keyhole surgery.

Once you are unconscious, the surgeon will make a series of small cuts in your abdomen and a telescopic camera and surgical instruments will be inserted into these incisions.

Surgical staples will be used to create a small pouch at the top of the stomach before the small intestine is joined to the pouch. Dissolvable stitches will then be used to close the incisions in the abdomen. The whole procedure will take around one to two hours to complete.

After the procedure is complete, you will need to rest and wait for the effects of the anaesthetic to wear off. You may need pain relief.

You should expect to stay overnight for a night or two. When you do leave the clinic, you must leave accompanied by a responsible friend or family member.

After having a gastric bypass, it will take a while for you to be able to eat solid foods again.

The day after your operation, you will only be able to drink fluids, little and often. This includes water, milk, squash, clear thin soup, tea and coffee. You should avoid drinking fizzy drinks.

You will then move on to a diet of puréed food, similar in consistency to smooth baby food. Adding extra liquid, like gravy or sauce, will help to make the food smoother and easier to swallow. Limit your meals to two or three tablespoons and make sure you eat slowly. You can then progress to mashed food.

Four weeks after your gastric bypass you should be able to eat lumpier foods, but you must continue to eat slowly and chew all your food thoroughly.

You will need frequent medical check-ups in the months following your gastric bypass surgery and will need to take vitamin supplements for the rest of your life in order to avoid complications such as malnutrition.

As part of your treatment with the Cadogan Clinic, you will have access to 24/7 on-call nurse assistance for the duration of your recovery.

The Patient Journey. A breakdown of what you can expect on your journey with us

We are deeply invested in ensuring that every step of your surgical journey with us is as informative and reassuring to you as it can be. This article outlines what you can expect at each stage of the journey

The Patient Journey

Frequently Asked Questions

Gastric bypass surgery is a fast and effective weight loss method for people who are obese and severely obese who have been unable to lose weight through diet and exercise alone.

The amount of weight lost after gastric bypass varies from person to person, but you can expect to lose around 70 percent of your excess weight within one year of surgery. Much of the weight loss happens within the first six months of surgery and stabilises after around 12 to 18 months. By losing this weight you will be cutting your risk of serious illness, such as heart disease and cancer, and any obesity-related conditions may go into remission, such as Type 2 diabetes and high blood pressure. Losing the excess weight will relieve the pressure on the joints, improving mobility and cutting the risk of musculoskeletal problems, such as osteoporosis and joint damage. Weight loss caused by gastric bypass surgery can also help to boost mental health, alleviating symptoms of depression and anxiety, further improving your quality of life.

However, to get the full benefit of your gastric bypass surgery, it is essential that you are able to commit to a healthy lifestyle after the procedure. This means following a diet and exercise plan. Your surgeon will discuss this with you in detail.

Some people who lose an excessive amount of weight may find that they have a lot of loose skin left behind. This can be successfully managed with abdominoplasty (tummy tuck) which is a surgical procedure that we also carry out here at the Cadogan Clinic. If you feel you would benefit from this surgery, one of our expert surgeons will be happy to speak to you about this in more detail.

As mentioned above, if you follow a sensible diet and exercise, you can expect to enjoy fast and effective weight loss following gastric bypass surgery. You can expect to lose around 70 percent of your excess weight within one year of surgery, according to figures from the The National Bariatric Surgery Registry.

Much of this weight is lost within the first six months and this tends to stabilise after around one year post-surgery. You may find you put a bit of weight back on at around 18 months after surgery, but this is normal. As long as the weight levels even out, this is not considered to be a problem.

Gastric bypass surgery costs in the region of £8,000 to £15,000 if you have your gastric bypass in the UK.

Don’t be tempted by cheaper prices at overseas clinics. Often clinics abroad do not adhere to the same high standards as in the UK and aftercare can be poor. We strongly recommend not going abroad for this type of surgery. It is not worth potentially putting your health at risk.

Here at the Cadogan Clinic, we offer the following as part of your gastric bypass surgery.

  • Up to two 60 minute consultations with a leading surgeon at our award-winning premises in Chelsea
  • Your procedure carried out at London’s leading specialist cosmetic surgery centre of excellence
  • 24/7 on call nurse assistance
  • Dedicated Patient Co-ordinator, as a personal point of contact through your journey with Cadogan
  • A pre-operative medical assessment to ensure you are fit for surgery 
  • Comprehensive post-operative aftercare courtesy of our specialist team.

It is possible to get a gastric bypass on the NHS, but there are strict criteria to meet and this can vary depending on which CCG (Clinical Commissioning Group) covers your area.

The NHS waiting list for weight loss surgery can be long and over the last two-and-a-half years Covid-19 has also had an impact on waiting times across the board. During this waiting time, any obesity-related conditions that you may have may get worse, further affecting your quality of life.

If you are looking to have your weight loss surgery done quickly, then the Cadogan Clinic has no waiting lists. If you are considering the Cadogan Clinic for gastric bypass surgery in London, then book an appointment with one of our experts who will be able to discuss the options with you.

A gastric bypass is a permanent weight loss surgery and is essentially irreversible. There is a revision procedure but there is a high risk of complications attached and this is only really carried out if absolutely necessary.

If you are unsure about permanent weight loss surgery then there are non-permanent alternatives available. This includes a gastric band, where a band is placed around the top of the stomach, and can be tightened, loosened or removed where necessary, and a non-surgical gastric balloon. In this procedure a balloon is placed in the stomach and filled with saline fluid, meaning there is less space in the stomach for food. Our expert surgeon can talk you through the options and help choose which would be the best to meet your needs.

Once you have had your gastric bypass surgery, it is vital that you maintain a healthy, balanced diet in order to help you reach your weight loss goals. As a gastric bypass operation makes you feel full more quickly, you will only be able to eat a small portion at each meal.

You should only eat a small amount of carbohydrates, but make sure that you are consuming enough protein. Avoid sugary foods, particularly as they may cause ‘dumping syndrome’. If you are suffering from dumping syndrome, you may feel sweaty, lightheaded and nauseous. This may progress to stomach pain and diarrhoea. This is caused by a change in blood sugar levels.

You should aim to drink around two litres of water a day, but try not to drink too much at mealtimes as this will fill you up. Avoid fizzy drinks.

You may find that you are intolerant to some foods after your gastric bypass. This intolerance may change over time, so you can always try these foods again at a later date.

Gastric bypass surgery is safe and the procedure is successfully carried out on thousands of people a year.

However you must consider that gastric bypass is a major surgery and comes with a higher risk of complications than other weight loss procedures, such as gastric banding or gastric balloon.

Complications may include food leaking from the join between the stomach and small intestine, blood clots, gallstones and malnutrition. However these are all rare and the benefits of gastric bypass surgery outweighs the risks.

Book a consultation with our expert surgeon who will be able to discuss the pros and cons of gastric bypass surgery with you and help decide whether this is the best weight loss surgery for you.

What are the risks of a Gastric Sleeve?

A gastric bypass is major surgery and comes with risks attached. Potential complications include:

  • Nausea and vomiting
  • Infection of the wounds
  • Chest infection
  • Bleeding from the operation site
  • Internal hernia
  • Bleeding from a stomach ulcer
  • A leak where the intestine is joined to the stomach. This can be very serious and will require an urgent operation.
  • Gallstones. You may develop these as a result of losing weight too quickly after surgery. Surgery to remove the gallbladder or prescription medicine after your gastric bypass may help.

General complications from any type of surgery include pain, scarring, blood clots (deep vein thrombosis) and an adverse reaction to the anaesthetic.

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We believe in the delivery of excellent outcomes and results, and exceptional levels of service. Our outcomes are natural and long-lasting, and we remain the premier choice for cosmetic surgery treatments in the UK.


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Laurel Wreath for Awards
Laurel Wreath for Awards


My Face My Body

Best Clinic Winner

Laurel Wreath for Awards
Laurel Wreath for Awards


My Face My Body


Laurel Wreath for Awards
Laurel Wreath for Awards


My Face My Body

Highly Commended

Laurel Wreath for Awards
Laurel Wreath for Awards


Aesthetics Awards

Highly Commended

Laurel Wreath for Awards

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