Weight loss surgery 


Understanding BMI results in adults

Find out how to calculate your body mass index (BMI) and interpret the results correctly.

Media last reviewed: 04/03/2014

Next review due: 04/03/2016

Body mass index and obesity

The most widely used method of seeing if you are a healthy weight is to calculate your body mass index (BMI). This is your weight in kilograms divided by your height in metres squared:

  • If your BMI is 25-29.9, you are over the ideal weight for your height (overweight).
  • If your BMI is 30-39.9, you are obese.
  • If your BMI is over 40, you are very obese (known as morbidly obese).

BMI does not provide an accurate assessment of weight in all circumstances, such as in people who are very muscular or children going through a sudden growth spurt.

Vicky Finch

'My gastric band surgery'

Vicky talks about the changes she had to make to her diet before and after weight loss surgery, and what it's like living with a gastric band

Weight loss surgery, also called bariatric surgery, is used as a last resort to treat people who are dangerously obese (carrying an abnormally excessive amount of body fat).

This type of surgery is only available on the NHS to treat people with potentially life-threatening obesity when other treatments, such as lifestyle changes, haven't worked.

Potentially life-threatening obesity is defined as:

  • having a body mass index (BMI) of 40 or above
  • having a BMI of 35 or above and having another serious health condition that could be improved if you lose weight, such as type 2 diabetes or high blood pressure

For people who meet the above criteria, weight loss surgery has proved to be effective in significantly and quickly reducing excess body fat. 

The National Institute for Health and Care Excellence (NICE) is currently considering lowering the threshold for weight loss surgery to a BMI of over 30 for people who have recently been diagnosed with type 2 diabetes.

However, it is always recommended that you try to lose weight through a healthy, calorie-controlled diet and increased exercise before you consider weight loss surgery, as surgery carries a risk of complications and requires a significant change in lifestyle afterwards.

Due to these associated risks, most surgeons, whether they are working privately or for the NHS, would only consider a person for surgery if there was a clinical need, and not just for cosmetic reasons.

Read more about who can use weight loss surgery.

Availability of weight loss surgery

Even if you are eligible for weight loss surgery, the demand for this surgery on the NHS is currently higher than the supply in many areas of the country. Therefore, there may be a considerable waiting list.

Weight loss surgery is also available privately. Prices are around: 

  • £5,000-8,000 for gastric banding
  • £9,500-15,000 for gastric bypass surgery

An increasing number of people are seeking treatment abroad as costs for private treatment are often cheaper in other countries, but this option should be considered carefully. For more information, see planned treatment abroad.

Types of weight loss surgery

The two most widely used types of weight loss surgery are:

  • gastric band, where a band is used to reduce the size of the stomach so a smaller amount of food is required to make you feel full
  • gastric bypass, where your digestive system is re-routed past most of your stomach so you digest less food and it takes much less food to make you feel full

Several other surgical techniques may be recommended in certain circumstances.

Read more about how weight loss surgery is performed.

Life after weight loss surgery

Weight loss surgery can achieve often impressive results in the amount of weight lost, but it should not be seen as a magic cure for obesity.

People who have had weight loss surgery will need to stick to a rigorous and lifelong plan afterwards to avoid putting weight back on or long-term complications.

This plan will include:

  • a carefully controlled diet
  • regular exercise

The rapid weight loss may cause relationship problems, for example with a partner who is also obese, and it may lead to unwanted loose folds of skin, which may need further surgery to correct.

Also, many people with mental health problems, such as depression or anxiety, find that these problems do not automatically improve because they have lost weight.

It is important to have realistic expectations about what life after weight loss surgery will be like.

Read more about life after weight loss surgery.


As with all types of surgery, weight loss surgery carries the risk of complications, some of which are serious and potentially fatal, such as:

A 2014 American review of over 157,000 patients found the overall risk of death, within 30 days of having any kind of weight loss surgery, is around 1 in 1000. The risk of death after having a gastric bypass was slightly higher.

However, certain risk factors, such as high blood pressure or a BMI of 50 or above, increase the risk of complications.

Read more about risks of weight loss surgery.


As long as a person is willing and able to stick to their agreed plan afterwards, surgery can effectively reduce their weight and treat conditions associated with obesity, such as diabetes.

Recent research carried out in America found that on average:

  • people with a gastric band will lose around half their excess body weight
  • people with a gastric bypass will lose around two-thirds of their excess body weight

Both techniques also lead to a considerable improvement (and sometimes a complete cure) of obesity-related conditions, such as diabetes or high blood pressure.

Read more about the results of weight loss surgery.

Page last reviewed: 05/05/2013

Next review due: 05/05/2015


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The 15 comments posted are personal views. Any information they give has not been checked and may not be accurate.

Lubelle81 said on 09 July 2014

I just discovered I have PCOS.. The weight started packing on when I was 19.. I'm 32 now.. I got very lucky to have one son..But this uncontrollable weight gain is too much it's depressing, every time I travel to work I want to jump in front of a train.. I talked this over with my GP, I begged him for a gastric bypass but instead he told me to get a dietitian and enter a gym, I don't want to be difficult but I choose to work as a cleaner to replace going to a gym.. Besides swallowing painkillers as if I was eating skittles, How else can I explain to my GP 12 years of Pain, and Depression is enough for me, I settle for a Gastric Bypass??

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Chezzybaby said on 15 March 2014

I had a gastric bypass on 23rd October 2013 and 5 months on and I am 6 stone 2llb lighter and have not looked back, providing you stick with what the hospital tell you and take ur medication and eat what they say you should be fine. Iv yoyo dieted for years battled with my weight iv researched thus operation to help me reach the right decision . The only part of the journey I didn't really like was having to have injections in my tummy for two weeks twice a day, but it was all go after they were finished. And I do not regret it one bit. Everyone is different but this op had mentally changed my whole outlook on food and drink, I no longer crave chocolate and diet Pepsi which was my downfall before. Good luck to you all considering to have the bypass xx

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cirelondiel said on 07 January 2014

I need help.
I am 22 years old, 5''10 size 26/28 and around 25/26 stone. As a child I was always bigger than the other children in school.
I have been on a diet most of my life even when I was small. relentlessly bullied all the way through school and still even now remarks and taunts are made. exercise is hard as I had a accident a few years ago and have nerve damage in the base of my spine and a curvature in the top. manic depression and anxiety disorders and a history of self harming and several attempts on my own life. I am seriously considering surgery but I need as much help and advice as you can give me.
Any advice or words of wisdom will be greatly appreciated.

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cirelondiel said on 07 January 2014

I need help.
I am 22 years old, 5''10 size 26/28 and around 25/26 stone. As a child I was always bigger than the other children in school.
I have been on a diet most of my life even when I was small. relentlessly bullied all the way through school and still even now remarks and taunts are made. exercise is hard as I had a accident a few years ago and have nerve damage in the base of my spine and a curvature in the top. manic depression and anxiety disorders and a history of self harming and several attempts on my own life. I am seriously considering surgery but I need as much help and advice as you can give me.
Any advice or words of wisdom will be greatly appreciated.

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GastricBypassSufferer said on 10 December 2013

As someone who has to live with a mother who has had the gastric bypass operation, I think people should be made aware of what the side effects are to having this surgery and how Gastric Surgery can be detrimental to your own health because what the surgeons tell patients before hand is not a reality and the operation should be banned under some sort of misselling in my opinion.

Firstly as a result of having a cut and shut of the digestive system, the food consumed is never digested properly, you will not absorb all the nutrition you need from the food which will ultimately be bad for your own health but as the food passes through in a undigested/incorrectly digested state, what goes down the loo, stinks.

I really cant emphasis enough just how bad this smell is and over time this smell will follow you around everywhere like an unchanged nappy!

Likewise your gaseous emissions or flatulence will also smell an order of magnitude worse than before surgery and you will always be planning to be around a toilet as you have far less control over your bowels as a result. If an app existed where you can see every public toilet on the planet, gastric bypass recipients will almost certainly download it. Secondly, if you choose to have this operation, you will become very ashamed of this smell (which is a negative effect on your already fragile mental health) and will spend massive amounts on air-freshener and perfumes. This means anyone else living in the home if they have not already, will develop breathing problems including asthma as a results of the copious amounts of artificial smells deployed in the building. The smell for me is so bad it triggers massive coughing sessions and as a result I have developed permanent ringing in my ears and a hernia from the excessive coughing caused ultimately by this surgery. This excessive use of air freshener is bad for everyone's health but the I doubt the Gastric Surgeons have thought that fair ahead!

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GastricBypassSufferer said on 10 December 2013

Part 2.

Thirdly as a taxpayer I dont see this Gastric Surgery recipient having changed what they eat contrary to the "careful eligibility checks" carried out by the NHS before hand. My mother still continues to pig out on doughnuts and other junk fund, which suggests to me obesity may be have some element of mental health issues after all what is comfort eating if its not eating in search of missing nutrients from the diet? Likewise I think its also worth pointing out most obese people are seriously deficient in Vitamin D, and studies show your weight will drop off when your get your levels up to 200nmol/L, so if you want a cheaper less invasive alternative, get your Dr to check your Vit D levels and get them up, at least to 100nmol/L, as Vit D helps your body repair itself, your taste for healthy food will increase until you crave eating healthy food and shun sugary foods. Some fatty foods are healthy because fat soluble vitamins need fat to be stored in, so when you eat some joints of meat, you will getting the fat soluble vitamins the animal has naturally built up so you will benefit from a a natural form of vitamin delivery.

So to anyone considering this surgery, its painful, and will leave you smelling and behaving like an incontinent for the rest of your life. And ask yourself do you really want that? At least check out the Vit D route for 1 year before hand as the science backs up my claims, but it also means the UK's GDP will decline as a Vit D is a lot less expensive than questionable surgery.

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BigIsBack said on 09 November 2013

Reading the experiences of everyone else here that somehow resembles my own experience I come to the conclusion that patients are not in the heart of the NHS ethos.

I really hope that the NHS will help every patient enjoy a healthier life.

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Soul Surfer said on 10 October 2013

I am a 34 year old female. I have always suffered from weight problems and tried all the diets that are around. I managed to shed some weight when I was younger, however now is so difficult. Recently, I have been diagnosed with low thyroid function and I am taking hormone treatment to regulate that. My current BMI is 33.9 (I weigh 98 Kilos) - height 5.7. I have also been diagnosed with hypertension and I am asthmatic. I am just worried that things might just get worse as I get older. I wonder whether the NHS can make exceptions when just BMI is not 35 or above. I do certainly have the High blood pressure which is considered a serious health condition. Does anyone know if these exceptions exist?

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H from Bedford said on 27 August 2013

I had a gastric bypass last year and I would urge anybody who has had problems with their doctor to try and see another doctor perhaps even another doctor at the same practice. It is scary going to the doctors but all doctors vary and it is always worth getting a second opinion. Princess Teacake - I do understand what its like - I would stress your family history of diabetes when you see the doctor - really hope it works out.

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PrincessTeacake said on 28 May 2013

I am writing this to ask for help. I'm a female, aged 24, and currently weigh in at 21.7stone with my height being 5.8. Well I have always had an issue with my weight being a size 12/14 at school then size 16-18 at college. And now rest at a size 22-24. I am very insecure and very depressed about my weight. I have been to the doctors many of times to be told I'm not big enough. Well I'm pretty sure 21stone is more then enough! I hate the way I look so much I don't even let my fiancé see me in the nude. I hate being like this, it's always been a big issue. I have depression and anxiety and I'm worried I'm going to get diabetes soon as my auntie and mum currently have it. I have tried many diets, slimming tablets and even going to the gym 3 days a week but my weight barely comes off. Most I've lost is 1stone and a half but had a bad day and my depression got the better of me and I put it back on In a matter of a few weeks. I'm In this viscous circle and I can't get out. What does it take for me to get a gastric bypass on the NHS??? I pay my taxes! I don't want to be thin to be a model or just like everyone else I want to be thin to be healthy to get my confidence back to wake up everyday and not cry!

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fussie said on 25 May 2013

Dear mysticalpickle. I read your post with real compassion your frustration and desperation are so evident. I wanted GB surgery but was encouraged by my family to try other methods as we lost a family friend in the operating room having this procedure. I tried many things as you have but I persevered with Lighter Life and now I am so glad I did, some packs were OK but generally I had to think of it at nutrition. Ultimately, all I was doing was eating what I could have done after surgery and the counsellor was fantastic helping me to make the changes I wanted in both my diet and lifestyle and enabling me to start thinking about me and food differently. I know that being morbidly obese is a lonely place but the support of the group and the management group that I still attend every now and then is worth it. I am so proud that I own the responsibility of my weight loss and it is mine alone not dependant on an NHS budget or a GP opinion, Weight management isn't about what you eat it is about how we use food for a variety of reason. I wish you all the luck in the world with weight loss but please don't let the GP door closing stop you from doing what you need to do,

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mysticalpickle said on 21 May 2013

Hi, im a 40 yr old mum, im 5ft 7, i now weigh 20stone. I suffer with Fibromyalgia, severe depression/ migraines, i have a wheat and glutten issue( some diet foods make me worse) Ive had an acl recon, ive damaged ligamemnts in one ankle, I suffer with Achillies tendonopothy on both feet/ankles, i suffer with plantar facilitus on both feet and ganglion syst on one foot which can not be removed, its hard to breath at times, I also have ligament damage on one of the shoulders and carple tunnel damage in one of my wrists after a car accident. my sciatica is in overdrive. I do not claim disability as i am not disabled enough lol I can not walk unaided, im sick of taking pills, i can not attend a gym due to the above conditions, i have tried 5 diets( cambridge, lighter life, slimming world, weightwatchers and diet chef) i am not working , not because I am not qualified or dont have the incentive, but medical conditions stop me and companies wont epmploy insurance risks or obese( fact). I have begged for help from my gp in the past, and they suggest the normal.(gym and healthy food) I dont smoke, dont do drugs nor do i drink. My mental and emotional state are so low, its hard to see myself live the rest of my life like this. I have 2 children and want to be around for them, grandkids etc to enjoy my life and etc. i dont have a personal life, everything is sooo painful, i desperatly need some help. Having read the types of op, bypass, band etc , i read about the balloon too. which is similar to the band but can be altered to fix the need of each person. im going up and up in weight, and its hard for us over weighties to keep weight off through daily routine. I have no friends for support and family is miles away. Can anyone suggest something, im not after sympathy or a magic wand, but i just cant get me wobbly bits off. Im quite scared to go back to my GP. Would i be a good candidate for these procedures? surely having a better lif, healthier life is better than struggles

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nata1ie said on 08 May 2013

Im 32 5' 3" and a bmi of 53 since i had my daughter when i was a size 10 ive suffered from extreme lower back pains which made me put the weight on as i can hardly walk with the amount of pain im in i dont leave the house as apart from the pain, ive gained a phobiia that everyones looking and laughing at me.
Ive tried excercise to get my weight down but because of the pain i cant do it so i asked my doctor for weight loss surgery and he refused im at a loss why did he refuse when im obviously needing the help !! I just dont know where to turn anymore, if this comment gets read then plz help me xx

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Marina3 said on 05 October 2012

I am 18 years old, 5"3 and 105kilos. My BMI is 41. I have always been big in my life due to many bad experiences during my early life. I have been to my doctor today to discuss my weight, they just told me what I have already been trying to do since I was 14. I have done every diet possibly, hypnosis (didn't work), calorie controlled diets, non carb diets, all have not worked. I have quite an active life style. Yet I also suffer with Asthma. My weight can extremly make me depressed and stop me from doing what I want to do. I really need medical help now, Please.

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gilboandco27 said on 07 August 2012

Why can't my 21 year old Son have the gastric band fitted when he is over 28 stones and lives in his bedroom all of the time because he is so afraid of what people think of him. Does he have to wait untill he has a heart attack, diabetes or a stroke. He fits all of the criteria and also his mental health now because of the fear of going out of the house. I had the gastric band fitted 7 years ago now and I lost 11 stones and kept it off. I wonder if anyone will respond to this letter?

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Lose weight

Weight loss resources to help you lose weight healthily, including the NHS 12-week diet and exercise plan

'Is weight loss surgery right for me?'

Find out whether weight loss surgery, including gastric band and gastric bypass, is right for you, and how it would affect your diet and lifestyle