Gastric Bypass Surgery

Everything you need to know about gastric bypass weight loss surgery, from experts in bariatrics.

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By Mr Rishi Singhal MBBS, MRCS, FRCS, MD

Last review: 21/05/2022. All content on this page is reviewed by a multi-disciplinary team lead by Mr Rishi Singhal.

Gastric Bypass Surgery Overview

What Is a Gastric Bypass?

Gastric bypass surgery is the most powerful form of weight loss surgery for people living with obesity. In short, gastric bypass surgery reduces the size of your stomach and redirects the digestive tract

Having a gastric bypass is the best weight loss surgery for patients with a high body mass index (BMI). On average most patients will lose weight of up to 80% of their excess weight after gastric bypass surgery. 

Alongside the weight loss, the gastric bypass can help reverse serious weight-related health conditions such as type 2 diabetes and PCOS. 


The Gastric Bypass Helps People Lose Weight By

  • The gastric bypass reduces the capacity of the stomach from full-sized into a small pouch, meaning you don’t need to eat as much to feel full
  • The pouch gets connected to the small intestine, bypassing the rest of your stomach and fewer calories are then absorbed.
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We have been doing the gastric bypass for over 18 years and our team made up of expert weight loss surgeons, bariatric nurses, patient care coordinators and patient support, has experience of over 5,000 procedures.

Patients can expect to lose about 70% of their excess weight within 2 years of surgery and those with health problems such as type 2 diabetes, sleep apnoea or reflux disease can expect an immediate improvement in their condition. Often, medication can be stopped immediately.

Above is a short video about the gastric bypass and how it works. In addition to covering the traditional Roux en Y gastric bypass, we also provide information about the Mini gastric bypass which is an alternative method of weight loss surgery that is growing in popularity.

Am I eligible for the gastric bypass?

There are many factors to consider for eligibility but we generally offer the gastric bypass procedure to those with a minimum body mass index (BMI) of 35.

The eligibility criteria that apply in private healthcare are a little different than those that apply in the NHS.

The reason is that the NHS eligibility criteria that is set by NICE (the National Institute for health and Clinical Excellence) has to balance the public health benefit with what the state can afford. 

In the private sector we are not faced with the same price restraints as patients are paying for their own procedure. This means that we can take decisions based purely on the available scientific data. For that reason we will generally consider patients with lower BMI than would be the case for the NHS.

The NICE guidelines state that patients will be eligible for weight loss surgery if they have a BMI above 40 or above 35 with at last one major co-morbidity. In addition patients will ned to follow and ‘pass’ a 6 – 12 month weight loss programme before they will be considered eligible for surgery. There will then usually be a waiting list.

The reality is that very few NHS Trusts apply these criteria and you may have read in the press that Trusts are applying their own, much tighter, selection criteria. This is because they do not have the resources needed to apply the NICE guidelines.

Some Trusts are limiting surgery to patients with a BMI over 50, to diabetics and/or to patients who don’t smoke.

At Healthier Weight, we generally consider sleeve surgery for patients with a BMI of 35 and above. You will need to have tried and failed with diets as a way to manage your weight and your weight will need to be having a negative effect on your every day life.

If you are of Asian ethnicity and/or you are a Type 2 diabetic we would consider surgery at a lower BMI. We will explain the eligibility criteria in more detail at your face to face consultation.

Patients can expect to lose about 80%  of their excess weight within 2 years of surgery and those with health problems such as type 2 diabetes, sleep apnoea or reflux disease can expect an immediate improvement in their condition. Often, medication can be stopped immediately.

The gastric bypass operation

The simplest way to describe bypass surgery, is to say that the stomach and bowel are ‘re-plumbed’ so that the food you eat goes into a reduced stomach before passing directly into the bowel a little further down the bowel than was the case before.


The bypass works in two ways. Firstly, by reducing the size of the stomach and so restricting the amount of food that can be eaten. We usually reduce the stomach’s capacity by as much as 90-95%. On this page we give a technical breakdown of how the procedure is done.

How much weight will I lose with the gastric bypass?

Of course, the main benefit people are seeking when they have bypass surgery is to lose weight. There are other significant benefits however, especially where improvements in health are concerned. Those people who are managing health problems associated with their weight can expect significant improvements after bypass.

Typically, we expect gastric bypass patients to lose 60-70% of their excess weight over a 2-year period, and most of this weight is lost in the first year after surgery*. You will see from our case studies that some people lose all their excess weight. 

To compensate there will be some who lose a little less. For this reason, 70-80% is a reasonable expectation. Weight loss results will differ from person to person and your results, especially in the long term, will depend on how well you are able to adapt your lifestyle and eating habits. Our bariatric aftercare team is vital to helping you learn and embed the skills needed to maximise and to maintain your weight loss (see before and after photos and stories from gastric bypass patients here).

Weight loss example

  • A 5ft 6in person weighing 17st (240lbs / 109kgs) has an ideal weight of about 11st (154lbs / 70kgs)
  • They are carrying excess weight therefore of 86lbs (240lbs actual weight minus 154lbs ideal weight)
  • 70% of 86lbs is around 60lbs
  • So, this person could expect to lose (on average) about 60lbs (27kgs).

Scientific evidence suggests that most gastric bypass patients who comply with the follow-up requirements, including nutritional recommendations, do very well, and see great long-term results*. Moreover, compared with obese individuals who have not had surgery, gastric bypass patients have a much lower risk of premature death and disability.

*JAMA. 2012 Jan 4;307(1):56-65. doi: 10.1001/jama.2011.1914. Bariatric surgery and long-term cardiovascular events

Success Stories
Real People, Real Stories, Real Lives Changed With The Gastric Bypass
Benefits & Risks

What are the Benefits of Having Gastric Bypass Surgery

Turning to the health benefits bypass patients can expect, it’s a long list and the improvements are usually very significant. In many cases people see a complete resolution of their symptoms for the problem they are managing.  Here are some of the more common weight related health problems and the benefit people can expect.**

As specialists in weight loss surgery we are familiar with all the health issues associated with obesity. It is also our duty to inform all our patients of the risks and potential complications of gastric bypass surgery, you can view these here. If you have specific health question, please do contact our team and we’ll be pleased to discuss them with you.

Video: How my health improved after weight loss surgery

**Buchwald H et al. Bariatric surgery: a systematic review and meta-analysis. JAMA. 2004 Oct 13;292(14):1724-37.

Cost & Finance

Gastric bypass cost and finance

At Healthier Weight we provide you with a fixed price gastric bypass package. With this package you have certainty of the cost of your treatment, including aftercare, blood tests and any treatment required in relation to a complication arising from your procedure. You can read more about our gastric bypass aftercare and support package here.


Put simply, it means you can go ahead with surgery safe in the knowledge that you will be faced with unexpected additional costs in the future.


The fixed price of your gastric bypass will vary depending on several factors including your location, the type of gastric bypass (primary or revision) and any special treatment requirements that are identified in the pre-operative period.


In order to help as many people as possible gain access to our services, we have developed a number of monthly payment plans plans tailored to the needs of our patients.


The importance of aftercare and support is often underestimated with the gastric bypass. Often people think the procedure is so powerful that they lose weight without too much effort, especially in the early months. However, over time the power of bypass will subside, and it will be the diet, eating and exercise changes that you have made in the years after your surgery that will help you maintain your weight loss.

Our team is here to see you in clinic and to provide the support you need for enduring success.

With this in mind, we have developed an aftercare and support package that we consider to be the most comprehensive of its type in the UK.

Our aftercare package has been developed to provide everything you need for success.

*Hosted on the Healthier Weight app


Gastric bypass common FAQs

This depends upon what you do for a living, but if you have a sedentary occupation you can generally expect to be back at work about 2 weeks after gastric bypass, after which time the wounds should have healed and you will be feeling more comfortable. If you have a physically demanding job involving lifting etc, you may need a little longer. The bowel and stomach inside your abdomen will be healed in around 6-8 weeks, so during this period it is important that you follow the nutritional guidelines as closely as you can.

Your long term success with your procedure is dependent on high quality aftercare. Anyone who has had weight loss surgery will tell you this is crucial. All too frequently, overseas surgery packages have no aftercare.

In the UK surgeon outcomes are monitored closely. There is a duty of candour and transparency. In many overseas countries the same standards do not apply.

We have seen many botched procedures from overseas that come with limited aftercare and warranties. You won’t receive any support from any serious problems that arise post-op, and you will ultimately go onto the NHS waiting list for your procedure to be put right.

Generally there is minimal scarring with a gastric bypass. The operating ports are placed in the abdomen through 5 narrow (0.5 cm) incisions which are sutured and/or glued and will normally heal in about 10-14 days. The scars should fade gradually. Some individuals have a greater tendency to form keloid which may result in thicker and more prominent scars.

You may eat most foods that don’t cause you discomfort. However, because you can only  eat small amounts, it is important to include foods rich in protein but low in fat and sugar. We encourage you to eat vegetables, fruit, wholegrains, lean meat and fish. You will be provided with detailed nutritional information following your gastric bypass surgery.

Mr Rishi Singhal MBBS, MRCS, FRCS, MD

Mr Rishi Singhal MBBS, MRCS, FRCS, MD

Mr Singhal is an expert bariatric surgeon based in the West Midlands and also Medical Director at Healthier Weight

Call our specialist team today on
0800 313 4618 
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