Added by Anne Beckett on 23.07.2020

What is Gastric Bypass Surgery?

Gastric bypass surgery belongs to the group of surgical procedures known as bariatric surgery.  This is a group of procedures which, in addition to gastric bypass surgery, also includes gastric band and gastric balloon procedures, amongst others.

Often these procedures are collectively known as weight loss surgery. They all have one thing in common – to make changes to the digestive system in order to help people lose weight.  Usually, this will mean reducing the size of the stomach and/or the small intestine.

So, what happens in a gastric bypass operation? There are a few different types of gastric bypass operations. The most common procedure is known as the roux-en-y gastric bypass. This involves the stapling part of the upper stomach to form a small pouch. This pouch is usually about the size of a thumb. Part of the small intestine is then reshaped (into a ‘Y’ shape) and attached to this small pouch.

There are other types of gastric bypass procedures which involve more invasive surgery but these are usually only used with exceptionally obese patents.

Usually, the surgery is performed laparoscopically. This means that small incisions are made in the abdomen and the operation is performed using a laparoscope – a rod with a tiny video camera and light at the end of it.

Desired results are not 100% guaranteed, however, generally, patients tend to achieve a significant weight loss.

Clinic Hunter gastric bypass

How does gastric bypass work?

Once the small pouch has been created, this means that the main part of the stomach has now been bypassed. Effectively the stomach has been extensively reduced in size. This results in the new ‘stomach’ (pouch) feeling full much faster than normal. In fact, should the person continue to eat, they will eventually feel quite sick and nauseous. In addition, because part of the small intestine has also been bypassed, the body will not absorb so many calories from the food. These two things combined, less food eaten and less absorption will lead to a weight loss.

Gastric bypass candidate

The question on many people’s lips these days is: how to lose weight ? Low-calorie meals, slimming clubs, diet programmes are all intended to help in the fight to lose weight. However, for some people, and for a variety of different reasons, none of these things may have been helpful in maintaining a long-term sustainable weight loss. This is often when bariatric surgery is considered.

Guidelines from the British National Health Service, the US National Institutes of Health, the Mayo Clinic, and many other organisations use the following guidelines when accepting a patient for gastric bypass surgery.

  • Candidates should have a Body Mass Index (BMI) of over 40 (Check out the Clinic Hunter BMI calculator)
  • Exceptionally those with a BMI of 35-40 may be accepted if they have a serious condition (e.g. type 2 diabetes or high blood pressure) which would improve with weight loss
  • Other weight loss methods have already been tried
  • The candidate agrees to healthy lifestyle changes

The candidate is fit and healthy enough to undergo a surgical operation

man reading book

Candidate for gastric bypass should have a BMI over 40. The gastric bypass procedure is a serious surgery and in most cases should only be considered after trying to lose weight through a healthy diet and exercise

The gastric bypass procedure is a major operation and in most cases should only be considered after trying to lose weight through a healthy diet and exercise.

In the past, gastric bypass surgery was not considered suitable for the over 60s. Nowadays, this is not considered a problem providing the candidate is fit and healthy enough to undergo an operation. However, most surgeons will only perform a gastric bypass operation on a person under 18 in very exceptional circumstances. There are some reports that in a very small number of cases this surgery may lead to an increased risk of suicide. The incidence is very small, nonetheless, it should be borne in mind particularly with those people already suffering from mental health issues.

The surgery is designed to be permanent and is very difficult to reverse.

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Gastric bypass vs gastric bypass - The difference between surgeries

What is a mini-gastric bypass?

The mini-gastric bypass procedure has become very popular in recent years. It was pioneered by Dr. Robert Rutledge in 1997. It is very similar to the roux-en-y gastric bypass, except that instead of creating a small pouch from the stomach, the stomach is actually stapled to form a narrow passageway which is then attached to the small intestine.

Comparison of mini gastric bypass vs gastric bypass


Mini Gastric Bypass

Gastric Bypass

Surgery Time (approx)
1-2 hours
2-3 hours
Surgery featuresminimally invasive, simpler, easier to reversemore invasive than the mini gastric bypass and is not designed to be reversed
Physical changesstomach is simply stapled to provide a partition, less re-routing of the small intestine and one less connection created, which means the risk of complications is lower
Stomach is actually separated. Carries the usual risks and complications associated with any surgery
Average weight loss (this will vary from person to person)About 50% of excess weight may be lost after 18 monthsAbout 50% of excess weight may be lost after 18 months
Major risk factorsevere acid reflux
Internal hernia
SafetyAll research points to the fact that this procedure is safe, however in medical terms it is a fairly new procedureGastric bypass is a very-well established procedure and there has been more research into its safety and effectiveness than other procedures

The mini-gastric bypass is growing in popularity. However, not all surgeons are trained in this procedure and long-term results are unclear. The bariatric surgeon will advise on the best surgery for a particular patient.

Clinic Hunter mini gastric bypass


How to prepare for the surgery

The bariatric surgeon will expect his/her patients to go on a gastric bypass pre-op diet. There are two main reasons for this. Firstly, the patient will need to follow a much-reduced diet after the operation, so it is very helpful to get used to this way of eating. Secondly, and probably most importantly, the liver needs to be ‘prepared’. When patients are overweight, this is usually caused by an excess of sugar and fat in the diet as well as overeating. This results in an enlarged and hard liver. In order to perform gastric bypass surgery laparoscopically, the surgeon needs to push the liver slightly to one side to access the stomach. The smaller and softer the liver is, the easier it is for the surgeon to do this. If the surgeon is not able to do this, he will then have to resort to much more invasive surgery, by cutting directly into the abdomen. This carries a higher risk of complications.

As always, it is better to take the advice of your surgeon and which diet he/she would recommend. Usually, the diet starts about 14 days before the planned date of the surgery. There are a few different pre-gastric diet plans which are often used.

  • Milk diet before gastric bypass – the milk diet, as its name suggests, consists of drinking 2 litres of milk a day. This is usually semi-skimmed milk, but may also be skimmed or sweetened soya milk. Non-sugar flavourings are allowed as well as unlimited water, tea, coffee, and unsweetened fruit drinks.
  • Under 1000 calorie diet plan before gastric bypass – as the name suggests this diet consists of minimising the calorie intake.
  • The Ketosis Plan diet before gastric bypass – this eating plan forces the body to burn fat instead of carbohydrates. Typically, about 70% of calories are derived from fat, less than 10 percent from carbohydrates s and less than 20 percent from protein.
  • The Soup, Yogurt and Milk diet before gastric bypass – this is also known as a liquid diet.
  • Protein shake diet before gastric bypass- eating only protein shakes commonly available in the shops.

This is just a selection and the surgeon will always advise on the best eating plan for the patient.


Gastric Bypass Procedure - how long does gastric bypass surgery take?

A gastric bypass procedure is stomach surgery and is done under general anaesthetic. As with all major operations the patient cannot eat for about 6 hours before the operation and only drink up to 2 hours before the operation. Admittance to the hospital will be the evening before or the morning of the operation. Gastric bypass surgery time is 1-3 hours depending on a variety of different factors. A mini gastric bypass will take up to about 2 hours.

Gastric Bypass Recovery and Aftercare

Two hands- taking care of someone

Gastric bypass recovery time is usually from two and five days and requires a special post-op diet

The in-hospital gastric bypass recovery time is usually between two and five days. Mini gastric bypass hospital stays are often a little less. There will be some pain at the sight of the surgery and, with a laparoscopy, there may be some shoulder and neck pain. The pain should be easily controlled with painkillers and, as with all operations, the patient will be encouraged to get out of bed and walk around as soon as possible to avoid complications such as blood clots. As with any post-operation wound, the area of the incision should be kept clean and dry.  Showers may be taken, provided care is taken not to get the wound/dressing excessively wet. Baths, however, which will saturate the area, are not a good idea until about three weeks after the surgery or after the wound has closed completely. For the first few days, the gastric bypass recovery diet will consist of clear liquids only – water, very thin soup, tea, coffee, sugar-free fruit juices, and ice lollies. This will allow the stomach to heal.

Diet after the gastric bypass surgery

Gastric bypass surgery is not a magic bullet, the patient will still need some willpower to commence a new eating regime. This regime will last for the rest of the patient’s life. The diet after gastric bypass will be introduced in stages and the surgeon or, more probably, the dietitian will give specific details of what can and cannot be eaten in the gastric bypass post-op phase.

Generally, the gastric bypass diet plan will look something like this:

Time period

What can be eaten

1-2 days after surgeryClear liquids only - as above
Up to 4 weeks after surgeryFull liquid diet - clear liquids plus milk drinks, protein drinks, ‘thin’ smoothies and yogurts
Up to 6 weeks after surgerySoft food can be introduced - pureed meats and vegetables
Up to 8 weeks after surgerySemi-solid foods = at this stage foods high in protein are more important than fruit and vegetables. Protein will help the body to heal.
After 8 weeksA ‘normal’ diet can be resumed with small portions and healthy choices of food- it will be necessary to experiment with foods to check your body’s tolerance

Life after gastric bypass will be different when it comes to food choices. The following tips may be useful:

  • It is essential to drink plenty of water
  • It will help to drink water 30 minutes before and 30 minutes after eating
  • Eating and drinking at the same time will cause the new ‘stomach’ to stretch, so always leave about half an hour between eating and drinking
  • Alcohol is not recommended because of its high calorific value, in addition, the body may react differently to it after a gastric bypass
  • It is essential to take vitamin and mineral supplements as the limited absorption may mean that the body does not extract these necessary nutrients from the food
  • Eat only small portions of food
  • Avoid high-fat and high-sugar foods

Remember that this eating plan is now for life. In consultation with a dietitian a long term diet after gastric bypass surgery will need to be formed. Exercise will also play a very important part in the lifestyle changes.

Gastric Bypass Results

Generally, results of gastric bypass procedures are good, however, they do depend on how well the patient controls their eating patterns post-surgery. It is possible to lose 50% or more of the excess weight within eighteen months. In turn, this weight loss may resolve or, at least, improve other health issues such as type 2 diabetes, osteoarthritis, heart disease, high blood pressure among others.

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Gastric Bypass Surgery side effects and complications

Any surgical procedure can carry a risk of side effects and complications and gastric bypass surgery, as a major surgical operation, is no different. It should be emphasised that the likelihood of these risks occurring is small, but they should be taken into consideration when thinking about gastric bypass surgery.

Gastric bypass surgery complications may include the following:



Infection of the woundIf this should happen - antibiotics will be prescribed to help the wound to heal correctly
Blood clots
These are a possible side-effect of any surgical procedure ad may occur in the legs or lungs. Blood thinner injections and/or compression stockings should help to avoid these
Excessive bleedingThis will also be managed during the operation
Allergic reaction to anaesthesiaThis will be managed during the operation

Other gastric bypass side effects long term include: gallstones, hernias, malnutrition, acid reflux and ulcers.

Anastomotic leak after gastric bypass

An anastomotic leak after gastric bypass surgery is possibly the most dangerous complication of this procedure. Although estimates of occurrence vary, research in Scandinavia in 2014 recorded anastomotic leaks occurring in 1.1% of patients.

An anastomosis is simply when two things are joined together. In a gastric bypass procedure, the new ‘stomach’ is joined to the small intestine usually at two points in the standard gastric bypass surgery and usually at one point in the mini gastric bypass surgery. Occasionally, digestive juices and partly digested food will leak out at these newly created connections. Often this occurs within a few weeks of surgery, however, it may happen up to several weeks afterward.

The more obese the patient is, the greater the risk of an anastomotic leak. Other risk factors include being male, having other medical problems besides obesity, and having a history of previous abdominal surgery.

Any signs of feeling unwell, such as fever, nausea, and stomach pain should be investigated immediately, so that appropriate action may be taken at once.

When weight loss surgery does not work

Apple with meter tape

The reason for not losing the weight after gastric bypass surgery may be not the following weight so it is worth to check it with a dietitian

Occasionally a small percentage of patients may find that they are not losing weight after gastric bypass surgery. Research in 2008 (Factors Associated With Poor Weight Loss After Gastric Bypass Surgery Identified) revealed that those people suffering from diabetes and whose new stomach ‘pouch’ was bigger had more issues losing weight. Often overweight people have other conditions that need to be controlled by drugs. This medication could also interfere with weight loss.

The amount of weight loss is also dependent on how strictly the patient sticks to their diet plan. The surgery, in itself, will not make the patient lose weight, it simply helps the patient to stick to a healthy diet.

So, in answer to the question – why am I not losing weight after gastric bypass surgery – the first thing to check is diet!


Alternatives to gastric bypass

Gastric bypass is only one type of bariatric surgery that is available.

Other types of surgery include:

  • Gastric balloon a soft balloon, filled with a saline solution is inserted into the stomach so the stomach feels fuller quicker
  • Gastric band – a band is placed around the stomach to reduce its size
  • Gastric sleeve – the size of the stomach is reduced by about 70% by creating into a thin vertical tube from part of it
  • Biliopancreatic Diversion with Duodenal Switch (BPD-DS) used for patients with a BMI over 40. It is done with two separate operations and is a more drastic procedure with bigger weight losses but also more complications.

Gastric Sleeve vs Gastric Bypass

The surgeon will always suggest, what in his/her opinion, is the best solution for the required weight loss and circumstances. In many respects, the gastric sleeve and gastric bypass procedures are very similar inasmuch as they both physically reduce the size of the stomach.

Our article on gastric sleeves provides more information about this procedure.

Gastric bypass or sleeve – let’s look at some differences in specific aspects:

HungerThe feeling of hunger is reduced more with the gastric sleeve
Vitamins/MineralsThe gastric bypass reduces the amount of vitamins and minerals the body can absorb- the gastric sleeve does not
ProcedureThe gastric sleeve is a less complicated procedure with a shorter operating time
RecoverySimilar recovery time for both procedures
Weight lossShort term very similar, but long-term those patients with gastric bypass maintain their weight loss for longer
Complications and side effectsGastric bypass has a slightly higher risk of complications and side effects

Gastric Bypass Cost

The cost of gastric bypass surgery in the UK will vary from hospital to hospital and within the different regions. The table below represents the average cost for an operation in the private sector and will often include follow-up consultations for up to 2 years.


Cost in British Pounds

Central London
East Midlands12,180
East of England9,965
Harley Street9,850
North East England12,800
North West England9,770
South East England11,130
South West England10,090
West Midlands10,785
Yorkshire and Humberside9,945

Source: Private Healthcare UK

Is gastric bypass refunded on the NHS?

Weight loss surgery is available on the NHS in the UK. Patients may be considered for NHS treatment if the following applies to them:

  • BMI of 40+, or between 35 and 40 for those with a serious condition which could improve with weight loss
  • Other weight loss methods including dieting and exercise have already been tried
  • The patient agrees to a long-term agreement to make healthy lifestyle changes and attend all follow-up sessions
  • The patient is fit and healthy enough to have a general anesthetic

Gastric bypass surgery is available on the NHS in the UK. Patients may be put on the list for the surgery if they meet the necessary requirements

How long does it take to get a gastric bypass on the NHS? – If the above conditions are adhered to, the patient may be accepted (through their GP) on an Initial Assessment Pathway. This may last up to 12 months and the patient will be expected to demonstrate that they are committed enough to lose around 10% of their body weight and to give up smoking if applicable. Assessments will also be made of current medical issues as well as psychological assessments. After 12 months, there is the possibility (not guaranteed) that the patient will be referred to a bariatric surgeon for possible surgery.

Ultimately, however, weight loss surgery is not a high priority for NHS funding, which currently has many other pressing calls on its budget. In addition to the actual operation, additional post-op aftercare and advice means the cost for each person is much higher than for other surgical operations which are deemed to be more pressing. The NHS waiting list in some areas may well be quite long. This will only get worse as numbers of NHS weight loss procedures are decreasing year on year.

Gastric Bypass Abroad - how much does it cost?

Many clinics in different countries offer gastric bypass surgery for foreign patients. While choosing the clinic patient should take into consideration a few things and choose the one which is fairly easy to travel to

Many countries can offer bariatric surgery much cheaper than in the UK. Weight loss surgery prices in Europe can be found for as little as £5,000 and even cheaper in places like India and Thailand.

When thinking about a gastric bypass procedure abroad, there are certain things to bear in mind. Firstly, for overweight passengers, air travel is not the most comfortable mode of transport and that may be made even worse when suffering from post-operative pain. Secondly, in the highly unlikely event that there is a subsequent problem, the surgeon needs to be fairly easily accessible. Thirdly, a gastric bypass procedure is a major surgical operation, so it pays to think about the qualifications of the doctor and the hygiene and facilities of the clinic/hospital. All of this leads to the conclusion that the best option for most people is to have surgery in a country which is fairly easy to travel to. For UK residents this would generally be a European country.

The overseas clinic/hospital will include a 4 or 5-night hospital stay in the cost. In addition to this most patients will need to book additional hotel accommodation for a few nights longer so final checks can be made on the healing process and so that they feel comfortable enough to sit on the plane for the journey home. What’s also important, patients can get secured for their medical trip, which makes their travel and stay abroad much safer. Clinic Hunter & AXA Partners have created a medical insurance for overseas dedicated solely to medical tourists.

Gastric Bypass in Poland

After its entry to the EU in 2004 Poland started welcoming more and more medical tourists. The private health sector is now a booming industry for Poland. It has some excellent medical facilities equipped with state of the art equipment. All surgeons are trained to a very high standard and English is spoken by many people in the medical professions.

Thanks to the recent emigration of Poles to other countries, there are very frequent and value-for-money flights available from all the major European cities. The flying time from the UK to Poland is around 2 ½ hours with prices starting at around £20 depending on the time of year and advance booking period. Additionally, the cost of living in Poland is lower than many western European countries, so hotel accommodation costs and extra expenses are lower.

For those patients who feel up to it after their hospital stay, or for anybody accompanying a patient, Poland has some excellent sightseeing opportunities. For gastric bypass surgery in Poland, additional aftercare services can be bought from providers in the UK or home country or patients can return to Poland for aftercare and dietary advice.

Prices for gastric bypass surgery in Poland start from around £4,000.

Gastric Bypass in Turkey

Medical tourism to Turkey is also growing year on year. Although flights are a little longer than to European cities (flight time London to Istanbul is almost 4 hours), it is still within comfortable reach.

Private medical facilities in Turkey are of an exceptionally high level, although as with all medical services abroad it pays to find out as much about the clinic as possible before making a decision. Surgeons are well-trained.

An additional advantage of some Turkish locations is that the extra days’ stay (after the initial hospital stay) can be spent relaxing on the beach.

Prices for gastric bypass surgery in Turkey start from around £3200.


size plus lady siting

Gastric bypass surgery is a life-changing decision. After the surgery patient can easily lose up to 50% of excess body weight after about 18 months of post-op instructions are followed correctly

Gastric bypass surgery is a major operation which is not easily reversed. Its effects will last for the entire life of the patient. The decision, therefore, to have a gastric bypass should not be taken lightly. The medical profession only recommends such drastic measures when BMI is 40+ or 35+ when other life-threatening conditions exist. On the other hand, for people who are severely obese and especially those who have other life-threatening diseases, a gastric bypass could be a lifesaver and/or extend life expectancy.

Gastric bypass surgery in itself is not a magic bullet and to ensure maximum results the patient must adhere to a strict eating regime that will last a lifetime.

As with all major operations some risks, although rare, do exist, and being overweight will always increase the risk for any operation. It is therefore important to take some steps to prepare the body for such a procedure by losing a little weight and ensuring the liver is in the best condition.

Obtaining a gastric bypass operation on the NHS is often difficult, so many people resort to a private procedure. Significant cost savings of up to about 60% can be made by going abroad, although with such major surgery it pays to find out as much as possible about the clinic/hospital and the surgeon to ensure that you will achieve the best possible care.

Overall results of the operation are good provided the patient adheres to a recommended eating plan. Actual weight loss will vary from person to person depending on personal circumstances, however, most patients can easily lose up to 50% of their excess body weight after about 18 months.

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BMI calculator:

Gastric bypass surgery and mental health:

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Gastric bypass vs mini gastric bypass:

Anastomotic leaks:

Reasons for not losing weight after gastric bypass surgery:

Cost of private gastric bypass operation:

NHS website on weight loss surgery:


Anne Beckett

In the UK Anne was a professionally qualified trainer with many years of experience in the training industry. She mainly worked in the travel, tourism and leisure industries (including Thomas Cook and British Airways) as well as in other sectors.

Since moving to Poland  twelve years ago, Anne has become involved in other business sectors – teaching English as a foreign language and translating documents from Polish into English. She specialises particularly,  in  medical translations and  works closely with dentists, cardiologists and neurologists in translating and preparing articles for publication. She has also trained as a practitioner in the field of neuro-linguistic programming and is a qualified hypnotherapist.

Any spare time is spent renovating the house in Poland which Anne bought some years ago.

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