Gastric bypass surgery

Reduces the size of your stomach and redirects the digestive tract.

We offer the latest surgical techniques to help you lose weight when diet and exercise haven't worked and your health is at risk because of severe obesity.

Sometimes also called

  • Roux-en-Y bypass

At a glance

  • Typical hospital stay
    2-5 nights

  • Procedure duration
    1-3 hours

  • Type of anaesthetic

  • Available to self-pay?

  • Covered by health insurance?
    Some insurers, by exception

Why Spire?

  • Fast access to treatment when you need it
  • Consultants who are experts in their field
  • Flexible payment options to help you spread the cost
  • 98% of our patients are likely to recommend us to their family and friends

What is gastric bypass surgery?

A gastric bypass, also known as a Roux-en-Y or restrictive surgery, is an operation your doctor may suggest if your health is at risk due to severe obesity.

The procedure involves reducing your stomach size, from 1500ml to around 30ml, and then connecting it to the lower part of your small intestine.

This restricts the amount of food you can eat and the number of calories you’re able to absorb through your small intestines. It also causes hormonal changes that deter you from eating unhealthy foods.

The benefits of gastric bypass surgery are:

  • Weight loss – on average people lose between 66% and 75% of excess weight in the two years after gastric bypass surgery
  • Improvements in any weight-related conditions you may have, such as type 2 diabetes, high blood pressure, high cholesterol, risk of stroke, heart disease, gastroesophageal reflux, sleep apnoea and polycystic ovaries
  • You're more able to do physical activity which can lead to increased energy, fitness, strength, stamina, bone density, improved mood and self-confidence

Your doctor may recommend gastric bypass surgery if:

  • You have a BMI of 40 or higher – this is known as ‘morbid obesity’
  • You have a BMI between 35 and 40 together with a serious condition that could be improved with weight loss
  • You’ve tried to lose weight through diet and lifestyle
  • You’re willing to have long-term follow-up appointments and adopt a healthy diet and lifestyle
  • You’re medically fit for surgery and anaesthetic

Your BMI can be calculated by using this equation: Weight (kg) ÷ Height (m)2

Your doctor may recommend gastric sleeve surgery first. This is an operation to reduce the size of your stomach without changing how your digestion works.

Gastric bypass surgery is not recommended for children and young people, and you may have to pass a psychological assessment first.

Alternatives to gastric bypass surgery include:

Find your nearest Spire hospital

Almost all our hospitals offer private gastric bypass surgery and have teams of bariatric (weight loss) consultants and surgeons who specialise in this procedure.

Spire Nottingham Hospital

How gastric bypass surgery works

Your surgeon uses surgical staples to make a small pouch at the top of your stomach and connects it to the lower part of your small intestine. This means the food that you eat will bypass the rest of your stomach and the upper part of your small intestine, going straight into your lower small intestine.

This helps you lose weight in three ways:

  • Restriction - you won’t be able to eat as much as before because there won’t be room in your new, smaller stomach pouch
  • Malabsorption - you’ll absorb fewer calories because your food will come into contact with less of your small intestine
  • Deterrent – you won’t feel like eating a lot of sugar because if you do, your body will produce too much insulin, making you feel light-headed and sick. This is called ‘dumping syndrome’

"The whole point of this surgery was to just live a normal life"

Colin, Imogen and Mary

Three bariatrics patients who underwent weight loss surgery at Spire Gatwick Park Hospital

Play video
View transcript of this video Hide video transcript

♪ [music] ♪- [Man] Sixteen months ago, I had a gastric bypass and I've lost eight stone. It's a journey that I didn't undertake lightly. -

[Woman 1] Well, mine was about four years ago now and I lost eight stone. I regained one, which is okay, but I absolutely love it. Doesn't stop me doing anything. In fact, it means I can do things I couldn't do before. - [Woman 2]

Exactly. It does the opposite, doesn't it?

- My biggest regret is not doing it sooner and why did I wait until I was 46?

- We're quite opposite. I mean, I literally researched it and then three days later booked in.

- Some people said to me, you know, "You're being selfish having a surgery. You should just go on a diet." But if just going on a diet was that easy... I've been on 30 or 40 diets.

- But we've all done it. We've been there.

- Yeah, it doesn't work.

- We've lost the weight, put it on plus more and that's just the way it goes, isn't it?

- I never, ever thought I was on a diet after the surgery. This was never about dieting ever again. I never want to be on a diet. The whole point of this surgery was just to live a normal life, eat how normal people eat, and become normal. And I've achieved my goal.

- When you think about how hard it is to be overweight, it's just not worth spending a second being that way. If you've got a choice and you can do it...

- The one thing I think we all have in common is we just wanted to be normal.

- Normal.

- Yes.

- Exactly.

- And for some people, it's normal again. For me, I've never been normal. I'd always been big since I was nine years old.

- There is a stigma with being big, whatever people say. People do...

- It's horrific.

- Yeah, yeah.

- I've been abused in the street for being overweight.

- Yeah.

- As soon as you lose that weight, you get this freedom.

- You can buy clothes in any shop you like.

- But also feeling comfortable again because I've never, ever felt comfortable in any kind of clothes, whether it be jeans or tops. Everything's too tight. It would stick to you. Especially in the summer, you'd feel uncomfortable.

- It's not about how we look. It's about how we are inside. It's got to be healthier for us and the older you get, the more important it is because you can't carry on being the weight that I was before without something going wrong. Whether it would have been joint issues or heart or turning diabetic. Something would have gone wrong if I hadn't addressed it like this.

- And I'm looking forward to my new life.

- Absolutely.

- My new life as the same person.

- You should actually look forward to it.

- As a normal person.

- It's great that we can talk to each other, as well, on that Facebook group chat so if somebody's got an issue, they can say something and the surgeon usually gets back within minutes. I don't know how he keeps up with it as much as he does.

- Knowing that, that support's in the background is one of the reasons that I had my surgery at Spire. ♪ [music] ♪

What to expect during gastric bypass surgery

Who will be involved?

As well as your bariatric surgeon, you'll also be seen by a:

  • Dietitian – to talk to you about your diet
  • Clinical Nurse Specialist
  • Anaesthetist – to administer anaesthetic during the operation

You may also be seen by a psychologist to talk to you about the emotional aspects of a gastric bypass and understand how we can support you through this process.

Before surgery

You’ll be assessed to check that you’re fit for the operation. This may include blood tests, X-rays and scans, as well as an explanation of the surgery and long-term outlook. You may need to lose weight and follow a calorie-controlled diet, low in carbohydrates and fats, to reduce the size of your liver. This is important for keyhole bariatric surgery as your liver will have to be moved out of the way so your surgeon can access the stomach. If your liver is smaller, the operation will be easier and safer. It’s advised that you stop smoking three months before your surgery.

You’ll be admitted to the hospital either the day before or on the day of your procedure. You shouldn’t eat for several hours before your gastric bypass, but you can continue to drink clear liquids until two hours before the operation. Should you need to stop any medication in preparation for your bypass surgery, your doctor will tell you. You’ll also have plenty of time to ask any questions and discuss your concerns before your surgery.

You may find it helpful to organise for someone to drive you home after your surgery and stay with you for a couple of days to help out while you recover.

During the surgery

A gastric bypass is a major operation so it’s carried out under a general anaesthetic, meaning you’ll be asleep.

It’s usually done by laparoscopic (keyhole) surgery, though this method isn’t suitable for everyone. Keyhole surgery has a much faster recovery time than traditional open surgery.

During the operation, your surgeon will:

  • Make small incisions (cuts) in your abdomen and pass through a tiny camera and instruments
  • Inflate your abdomen with carbon dioxide gas
  • Use surgical staples to make a pouch, about the size of a walnut, at the top of your stomach
  • Cut your small intestine and attach the lower part of it directly on to your new pouch
  • Join the remainder of your stomach and upper small intestine to the lower part – so digestive juices from your stomach can drain out
  • Close your incisions

If your surgeon thinks keyhole surgery isn’t suitable for you, they may suggest open surgery, which involves making one single, much larger cut.

How long does a gastric bypass operation take?

Between one and three hours.

Pain after gastric bypass surgery

It’s normal to feel some pain and discomfort after gastric bypass surgery, though it’s different for everyone. You’ll be given pain relief to help you.

Your hospital stay

You’ll usually be in hospital between two and five nights. After your surgery, you’ll be given compression stockings or blood-thinning medication to reduce your risk of blood clots which can lead to complications such as deep vein thrombosis (DVT) and pulmonary embolisms. You’ll stay until you have completed your X-ray normal swallow test and started your diet plan, this can be a further one to two days.

You may find it helpful to have someone drive you home and stay with you for a couple of days after your operation, while you recover.

Q & A

Simon Monkhouse, Consultant Upper GI and Bariatric Surgeon

Talking about gastric bypass surgery

Play video
View transcript of this video Hide video transcript

What is gastric bypass surgery?

A gastric bypass is a weight loss surgery procedure that essentially involves cutting the stomach into a small pouch, so it’s a small stomach out of your big stomach, and it also involves rerouting the small bowel. So there are two aspects to it.

How does it work and who is suitable for it?

It’s a very powerful weight loss tool and the mechanisms of action are hormonal and chemical. If your BMI is 35 or above and you have a weight-related problem such as diabetes, high blood pressure, breathing issues etc, then you may be suitable for a gastric bypass.

Is gastric bypass surgery suitable for type 2 diabetics?

It’s a particularly good operation if you’re type 2 diabetic as we would expect most diabetics to get off all treatment after a bypass operation.

What happens before the procedure?

So once you’re deemed suitable to go ahead, you’ll meet the multidisciplinary team which is really important to us at Spire. You’ll see the dietitian, the psychologist, the nurse specialist, and you’ll have a camera test down your throat into the stomach, pre-surgery, just to make sure everything is okay.

How long does gastric bypass surgery take?

The operation itself takes about two hours and you may have to stay in hospital for one to two nights.

Is gastric bypass surgery successful?

I would expect most bypass patients to lose about 90% of their excess weight at 12 months and I would say most patients achieve this.

Recovering from gastric bypass surgery

Recovery time

You should be back to your normal activities by six weeks after following a controlled diet but may experience changes as your body reacts to rapid weight loss in the first few months. This includes symptoms such as aches, tiredness, dry skin, feeling cold, thinning hair and mood changes. After three to six months you should be experiencing less of these symptoms and you’ll have lost most of your weight around two years after your surgery.

Aftercare and ongoing treatment

Your recovery care will include:

  • Pain relief
  • A review of any medicines you’re taking for weight-related conditions, such as diabetes or high blood pressure
  • A carefully controlled diet plan for the first four to six weeks, moving from liquids to pureed, soft then solid foods, plus advice on eating and portion sizes
  • An exercise plan to help speed your weight loss and improve your fitness
  • Blood tests to check if you need extra vitamin and mineral supplements
  • Discharge medication – which can include vitamin D, calcium, multivitamin A-Z with iron, vitamin B12, Lansoprazole
  • Follow-up appointments

Your lifestyle after treatment

The surgery won’t stop you craving or eating unhealthy food, so you must be willing to make long-term lifestyle changes.

You also won't be able to eat until you’ve had an X-ray and swallow test. After this, you’ll be able to eat soft foods at first and your dietitian will give you a comprehensive diet plan for the weeks after your surgery.

You’ll need to wear compression stockings for the two weeks after your surgery to prevent blood clot formation. You can shower but must not bathe for a week, and you must ensure that all dressings are kept clean and dry. You’ll need to attend follow-up appointments for the rest of your life. Eventually, these may just be annual checks to make sure your bypass is working properly. You’ll also have blood tests at regular intervals for the first two years after your surgery.

You can expect to return to work between two to four weeks after your surgery, though this depends on how strenuous your job is – you’ll have to request a fit note from your ward doctor should you need one. You can usually drive within two weeks of your surgery, but you should check your policy first.

You should keep active after your operation to reduce the risk of blood clots forming, however, you should try to avoid any abdominal or heavy exercises for at least six weeks.

As you start to lose weight after your bypass surgery, your body will need more protein to maintain your muscle mass and have a healthy metabolism. You’ll need to increase the amount of protein in your diet otherwise your body will start to rely on the protein from your muscles which will weaken them.

Avoid drinking at the same time as eating to prevent vomiting and dumping syndrome. This is an uncomfortable set of symptoms caused by the food in your stomach being too sugary, or quickly washed into the small intestine through the join. Ensure that you're drinking plenty of water throughout the day to prevent constipation.

If you’re planning to travel by plane within a few months of surgery, you should speak to your doctor first. Some complications may occur including deep vein thrombosis (DVT).

You can continue to have sex when you’re ready but you should avoid becoming pregnant during the first 12 to 18 months after surgery. Your nutritional levels are likely to be low during this time, which could harm your baby.

Side effects

You may find that you start to lose some hair, or it becomes thinner after your weight loss. Although this can be distressing, it is only temporary and will usually improve after a few months. You may also find that your skin becomes very dry after your gastric bypass surgery, you can improve this by drinking plenty of fluids, taking your multivitamins and applying a good moisturising cream regularly.

As your body reacts to rapid weight loss in the first three to six months, you can also experience body aches, tiredness, flu-like symptoms, feeling cold and mood changes.


The amount of weight you lose depends on your change in lifestyle habits, though you can expect to lose up to 90% of your excess weight within one year of surgery. As well as your weight loss, you may find that your gastric bypass surgery will improve other conditions related to being overweight including heart disease, high blood pressure and joint pain.

Risks and complications of gastric bypass surgery

Most people have gastric bypass surgery without complications, but all surgery carries some risks. Your consultant will explain them to you before you go ahead.

Gastric bypass complications can include:

  • Blood clots
  • Infection
  • Food leaking from the join between your stomach and small intestine, or the gut becoming blocked or narrowed
  • Nutritional deficiencies
  • Gallstones
  • Folds of skin due to rapid weight loss – further surgery can remove them
  • Changes in mental wellbeing such as depression and maladaptive eating
  • Regaining weight and the recurrence of obesity-related illnesses
  • Breathing problems
  • Stricture – where the connection between the stomach and intestine narrows
  • Deep vein thrombosis (DVT) and pulmonary embolism

Although rare, anaesthetic complications can include:

  • Chest infections
  • An unexpected reaction to the anaesthetic

You should call the hospital you had your procedure at or seek medical advice if you experience any of the following after surgery:

  • Stomach pains that don’t go away or get progressively worse
  • Fast heartbeat
  • High temperature
  • Chest pains or shortness of breath
  • Vomiting or vomiting blood
  • Difficulties in swallowing
  • Dark or sticky faeces
  • Wound infection – pain, redness, swelling or pus

At Spire hospitals, your safety is our top priority. We have high standards of quality control, equipment and cleanliness and a rigorous system of review and training for our medical teams.

Treatment and recovery timeline

Although everyone’s different, here’s a typical recovery timeline for gastric bypass surgery:

View interactive timeline View full timeline

2-5 days

Able to leave hospital

4-6 weeks

Follow a controlled, monitored diet

4-6 weeks

Back to most activities and some weight loss

3-6 months

Less symptoms of rapid weight loss

2 years

Most weight loss will have happened

  • 2-5 days

    Able to leave hospital

  • 4-6 weeks

    Follow a controlled, monitored diet

  • 4-6 weeks

    Back to most activities and some weight loss

  • 3-6 months

    Less symptoms of rapid weight loss

  • 2 years

    Most weight loss will have happened

What is dumping?

Dumping syndrome is a collection of uncomfortable symptoms, such as feeling sick, weak, faint, sweaty and diarrhoea, caused when sugary foods move from your stomach into the small intestine too quickly. You can avoid drinking and eating at the same time to help prevent dumping syndrome.

What can I eat after surgery?

After surgery, you’ll not be able to eat until your X-ray and swallow test. At first, you’ll have to eat a soft diet and your dietitian will give you a diet plan for the weeks after surgery.

Can I have excess skin removed?

As you lose weight after your gastric bypass surgery, you may find that you have excess skin on your body, particularly around your stomach, chest, hips and limbs. Surgery can be used to remove this excess skin, though this is normally considered to be a cosmetic procedure.

What qualifies you for gastric bypass surgery?

To receive gastric bypass surgery, you must either have a body mass index (BMI) of 40 or higher, or a BMI between 35 and 40 and a serious condition that could be improved with weight loss.

Your BMI can be calculated using this equation: Weight (kg) ÷ Height (m)2

You must have also tried to lose weight through diet and lifestyle, and be willing to have long-term follow-up appointments and adopt a healthy diet and lifestyle. You’ll also need to be medically fit for surgery and anaesthetic.

How dangerous is gastric bypass surgery?

Gastric bypass surgery is a common procedure and most people have it without complications, but all surgery carries some risks. Your consultant will discuss potential risks and complications with you before the operation.

How much weight can you lose with gastric bypass surgery?

Most patients can expect to lose up to 90% of their excess weight in the 12 months after their surgery, but this is dependent on adopting a healthy lifestyle after the procedure.

Can you put weight back on after a gastric bypass?

The surgery won’t stop you craving or eating unhealthy food, so you must be willing to make long-term lifestyle changes to avoid putting weight back on.

How long are you off work after gastric bypass surgery?

Depending on how strenuous your work is, you may need to recover for two to four weeks before returning to your job.

Is gastric bypass surgery permanent?

Gastric bypass surgery is generally non-reversible. However, if you do not adopt a permanent healthy lifestyle after the procedure, there is a risk of you reversing your weight loss.

Can you drink alcohol after gastric bypass surgery?

It’s not recommended that you drink alcohol for the first six months after your gastric bypass surgery, and you’ll feel the effects of the alcohol much more quickly than before as your stomach will absorb it differently. Alcohol is also high in calories and can stimulate your appetite.

Why is caffeine bad after gastric bypass surgery?

It’s okay to drink caffeine after your gastric bypass surgery, but you should avoid drinking too much as it acts as a diuretic and can cause dehydration.

What medications can you not take after a gastric bypass?

You should avoid taking a class of medication known as non-steroidal anti-inflammatory drugs (NSAIDs) as these can irritate your stomach and cause stomach ulcers. Common drugs that are NSAIDs include aspirin and ibuprofen. Your doctor will discuss in detail with you what medication you can and can’t take.

How much water can you drink after a gastric bypass?

You should try to stay hydrated throughout the day after your gastric bypass surgery while avoiding fizzy and sugary drinks. Your dietitian will advise you on what you should be drinking in detail.

What happens if you don't get enough protein after bariatric surgery?

As you start to lose weight after your bypass surgery, your body will need more protein to maintain your muscle mass and have a healthy metabolism. If you don’t have enough protein in your diet, your body will start to rely on the protein from your muscles which will weaken them.

Can a gastric bypass cause low iron?

After your surgery, your stomach may start to digest things differently, including the iron in your foods. You may need to take iron supplements during your recovery to prevent any deficiencies, your doctor will advise you.

The treatment described on this page may be adapted to meet your individual needs, so it's important to follow your healthcare professional's advice and raise any questions that you may have with them.

Get in touch


Marketing Information

Spire would like to provide you with marketing information about products and services offered by Spire and by selected third-party partners. If you do not consent for us to process your personal data for marketing activities, we will still be able to contact you about your enquiry.

We may contact you by email, SMS or phone about your enquiry. If we try to contact you by phone (mobile and/or landline) and you are not available, we may leave you a voicemail message. We may also use your details to contact you about patient surveys we use for improving our service or monitoring outcomes, which are not a form of marketing.

Submit my enquiry