Bariatric Surgery

Authored by , Reviewed by Dr John Cox | Last edited | Meets Patient’s editorial guidelines

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This article is for Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Weight Loss Surgery article more useful, or one of our other health articles.

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Treatment of almost all medical conditions has been affected by the COVID-19 pandemic. NICE has issued rapid update guidelines in relation to many of these. This guidance is changing frequently. Please visit to see if there is temporary guidance issued by NICE in relation to the management of this condition, which may vary from the information given below.

Bariatric surgical procedures are an option for treating severe obesity, by reducing intake or absorption of calories. There are various options, all of which have potential complications. A 2014 Cochrane review concluded that surgery results in greater improvement in weight loss outcomes and weight-associated comorbidities compared with non-surgical interventions, regardless of the type of procedures used.[1]Bariatric surgery should always be performed in a specialist centre and long-term follow-up of patients is necessary.

The number of procedures rose sharply by 70% between 2008/2009, although recording and coding changes contributed to this.[2]In England, in 2012/13, annual Health and Social Care Information Centre (HSCIC) statistics show over 8,000 were performed.[3]Many more surgical procedures are carried out on women than men (in 2012/13, 6,080 for women and 1,944 for men).

For more general information regarding obesity and its management, see separate articles Obesity in Adults and Obesity in Children.

Bariatric surgery is an option in severely obese patients, where lifestyle and medication have been evaluated but found not to be effective. Surgery can be combined with other treatments. Referrals are usually made via a specialised obesity management service. There are clear guidelines from the National Institute for Health and Care Excellence (NICE) about who should be considered for bariatric surgery. In the 2014 update of the guidelines, recommendations for earlier consideration of bariatric surgery for those people with diabetes mellitus were introduced. Prior to this, a report from the Office of Health Economics suggested that the number of procedures performed is far less than could be predicted from UK obesity prevalence figures and that commissioners of services are not complying with the guidelines or are interpreting them too stringently.[5]

  • BMI ≥40 kg/m2 OR BMI 35-40 kg/m2 with other significant disease (eg, type 2 diabetes, hypertension) that could be improved by weight loss and:
    • All appropriate non-surgical measures have failed to achieve or maintain adequate clinically beneficial weight loss.
    • They are receiving or will receive intensive specialist management.
    • They are generally fit for anaesthesia and surgery.
    • They commit to the need for long-term follow-up.
  • As a first-line option if BMI of >50 kg/m2 and surgical intervention is considered appropriate (and consider orlistat before surgery if the waiting time is long).
  • For people with recent onset (within the previous ten years) type 2 diabetes mellitus:
    • If BMI ≥35 kg/m2, expedite assessment for bariatric surgery (as long as they will receive assessment in a specialist tier 3 service.)
    • Consider assessment for bariatric surgery in a tier 3 service if BMI is 30-34.9 kg/m2.
    • For those of Asian origin, consider assessment for bariatric surgery in a tier 3 service at lower BMI than other populations.
Young people
Surgery is not generally recommended, as it is fraught with ethical issues and the potential long-term benefits and complications are not yet known.[6]NICE suggests that it may be considered in exceptional circumstances, if:
  • They have achieved or nearly achieved physiological maturity.
  • They are receiving or will receive intensive specialist management. This will include
    • Full information on procedures available and risks and benefits.
    • Management of comorbidities.
    • Psychological support before and after surgery.
    • Regular postoperative assessment, including specialist dietetic and surgical follow-up
    • Information about access to plastic surgery, such as apronectomy, where appropriate.
    • Access to suitable equipment for obese young people.
    • Assessment of fitness for anaesthesia and surgery.
  • They have had a comprehensive psychological, educational, family and social assessment before undergoing bariatric surgery.
  • They have had a full medical evaluation, including genetic screening or assessment before surgery to exclude rare, treatable causes of obesity. They should also have had a specialist assessment to exclude eating disorders.

There are increasing demands for bariatric surgery to be considered as a valid option in children and adolescents in the face of the increasing prevalence of obesity in this age group.[7]

Some research suggests that it may also be worthwhile for those with a BMI of 30-35.[8]Few procedures are performed on the elderly but the risk is thought to be no higher than any other gastrointestinal procedure.[9]The risk:benefit ratio for those with a BMI >70 is currently being researched but one study of 49 patients reported that it was a safe procedure.[10]

  • Unfit for surgery.
  • Uncontrolled alcohol or drug dependency.
  • Uncontrolled emotional disorders.
  • Lack of ability to understand surgery, consequences, need for follow-up.
  • Some centres advise pre-operative psychiatric and nutritionist assessment.
  • Procedures are classified as restrictive, malabsorptive or both.
    • Restrictive procedures produce a feeling of fullness with lower food intake.
    • Malabsorptive procedures limit calorie uptake from the intestine.
    • It may be that these methods of action overlap, and that the effect is physiological, via endocrine and neuronal means, rather than purely limiting calorie intake.
  • There are various procedures and variations on them, and these have evolved over a period of 50 years. The vast majority are now performed with a minimally invasive or laparoscopic approach.

Bariatric surgery procedures currently used

  • Restrictive:
    • Laparoscopic adjustable gastric banding.
    • Vertical sleeve gastrectomy.
  • Malabsorptive:
    • Biliopancreatic diversion with/without duodenal switch.
  • Both restrictive and malabsorptive:
    • Roux-en-Y gastric bypass (RYGB).
    • Other types of gastric bypass.
  • Other procedures:
    • Gastric stimulation.
    • Intragastric balloon.

Choice of procedure[4]

Bariatric surgery should be performed by a specialised team in a tertiary centre. The choice of procedure is partly determined by local expertise; it is important that all operations be performed by an experienced surgeon in a specialised multidisciplinary unit. Factors to take into account are:

  • Fitness for surgery.
  • Degree of obesity.
  • Goals.
  • Comorbidities.
  • Best available evidence about effectiveness and long-term effects.
  • Facilities available, and experience of surgeon.
  • Some centres have a two-stage approach, using a restrictive procedure initially, followed by a malabsorptive procedure later if necessary.

The use of the laparoscopic sleeve gastrectomy has increased in recent years.[15]The most commonly used procedures in the UK currently are laparoscopic adjustable gastric banding, sleeve gastrectomy and gastric bypass.[2]

Many studies and meta-analyses have tried to make comparisons between available procedures. The Cochrane review of 2014 concluded that outcomes were similar between RYGB and sleeve gastrectomy, and both of these procedures had better outcomes than adjustable gastric banding.[1]In those with very high BMI, biliopancreatic diversion with duodenal switch were found to result in greater weight loss than RYGB. It was noted that across all studies adverse event rates and re-operation rates were generally poorly reported, and the long-term effects of surgery remain unclear.

Explanation of bariatric procedures

  • Laparoscopic adjustable gastric banding: places a constricting ring around the stomach, below the gastro-oesphageal junction. The bands incorporate an inflatable balloon which can adjust the size of the ring, to regulate food intake.
  • Sleeve gastrectomy: most of the stomach is removed, leaving a sleeve-shaped cylinder of stomach with reduced capacity. This procedure is irreversible.
  • Gastric bypass: creates a small gastric pouch (restrictive) joined to the jejunum, bypassing the duodenum and proximal jejunum (malabsorptive). The RYGB is the usual procedure at the current time.
  • Biliopancreatic diversion: is a more extensive form of the gastric bypass, with the gastric pouch joined to the ileum, totally bypassing the duodenum and jejunum. It produces more extreme malabsorption.
  • Duodenal switch: biliopancreatic diversion is sometimes performed with a duodenal switch. This produces a short distal length of small intestine, severely limiting caloric absorption. This is a complex operation which takes some hours to complete.
  • Gastric stimulation: uses an implanted pacemaker-type device to produce electrical gastric stimulation, thought to cause a feeling of satiety.
  • Intragastric balloon: this is an endoscopic rather than surgical procedure, placing a silicone balloon inflated in the stomach to promote a feeling of satiety. There is insufficient evidence to assess its effectiveness and there have been complications such as gastric erosions and ulcers. It is therefore usually removed after six months.
  • Endoscopic techniques: apart from balloon insertion, various other endoscopic procedures are being developed but are not currently in common NHS use. These are collectively known as primary obesity surgery endolumenal (POSE).[16]

Those who have had bariatric surgery should be followed up by the specialist bariatric service for a minimum of two years. This should include:

  • Monitoring nutritional intake (including protein and vitamins) and mineral deficiencies.
  • Dietary and nutritional advice and support.[17]
  • Physical activity advice and support.
  • Psychological support.
  • Monitoring for comorbidities.
  • Medication review.
  • Information about professionally led or peer-led support groups. For example, the British Obesity Surgery Patients Association (BOSPA).

After discharge from bariatric surgery service follow-up, ensure that all people are offered at least annual monitoring of nutritional status and appropriate supplementation according to need. The

British Obesity and Bariatric surgery society (BOMSS) website has guidelines for GPs to help assess the significance of post-operative symptoms for the most common procedures in the days, weeks, months and years after surgery.[18]

  • Weight loss. In a long-term Swedish trial, weight loss averaged 18% after 20 years.
  • Remission of diabetes mellitus. The Swedish trial showed a 72% remission rate two years after surgery.
  • The Swedish study also reported a reduction in overall mortality of 29%, and a reduction in the incidence of myocardial infarction, stroke and cancer.
  • Evidence suggests that non-alcoholic fatty liver disease (including steatosis, steatohepatitis and fibrosis) appears to improve or completely resolve in the majority of patients after bariatric surgery-induced weight loss.[20]

Pre-operative discussion is important; patients may have unrealistic ideas about the amount of weight they are likely to lose, the need for follow-up and the potential complications. Peri-operative mortality is low at less than 0.3%, and is declining.[21] The incidence of complications within the first six months varies from 4-25%, and depends on procedure used, duration of follow-up and individual patient characteristics. Complications to consider include:

  • Peri-operative complications as for any abdominal surgery include venous thromboembolism. The use of prophylaxis has reduced the incidence of deep vein thrombosis and pulmonary embolism considerably.[22]
  • Possible complications of banding are band slippage, leakage, infection or migration.[23]
  • Surgical complications of bypass surgery include leakage or stenosis of the stoma, gastrointestinal ulcers or bleeding, small bowel obstruction and hernias.
  • Nausea and vomiting may occur due to overeating or to stenosis at the surgery site.
  • Dumping syndrome: symptoms are flushing, light-headedness, palpitations, fatigue and diarrhoea, typically triggered by sugar after a RYGB. It is a neurohormonal reaction. It may help to discourage overeating.
  • Malnutrition: micronutrient deficiencies are a recognised problem, especially with malabsorptive procedures. Iron-deficiency anaemia is the most common complication. Calcium, zinc, folate and vitamin D deficiencies can occur. Thiamine, B12 and copper deficiencies may cause neurological symptoms and should be remembered. Protein-calorie malnutrition can also occur. Long-term follow-up is important.
  • Gallstones can develop as a consequence of rapid weight loss.[24]
  • Hyperoxaluria which can be mitigated to some extent by aggressive fluid intake, oral calcium and citrate supplementation.
  • Inadequate weight loss and weight regain. The latter is affected by behavioural patterns that can be assessed pre-operatively in order to identify individuals particularly at risk.[25]
  • Up to 35% may require revisional procedures, particularly in gastric banding.
  • Bariatric surgery patients show a higher suicide rate than the general population.[26]
  • Removal of excess skin after significant weight loss may not be available on the NHS.

The National Confidential Enquiry into Patient Outcome and Death (NCEPOD) report

The NCEPOD report on bariatric surgery was published in 2012. In order to reduce mortality and morbidity associated with bariatric surgery, the following initiatives were suggested:[2]

  • Surgeons should undergo a minimum number of procedures before being allowed to operate unsupervised.
  • Service provision should be restricted to a number of accredited centres with a set minimum number of procedures per annum.
  • All patients must have access to the full range of specialised professionals appropriate for their needs in line with NICE guidelines.
  • Psychological support should be initiated at an earlier stage in the process.
  • Consent should be a two-stage process and should not be taken on the day of surgery.
  • A clear discharge plan should be provided to the GP as soon as possible, including detailed dietary advice.
  • Postoperative psychological advice should be made available if required.

Further reading and references

  1. Colquitt JL, Pickett K, Loveman E, et al; Surgery for weight loss in adults. Cochrane Database Syst Rev. 2014 Aug 88:CD003641. doi: 10.1002/14651858.CD003641.pub4.

  2. Too Lean a Service?; National Confidential Enquiry into Patient Outcome and Death, 2012

  3. Statistics on Obesity, Physical Activity and Diet: England 2014; Health and Social Care Information Centre (HSCIC)

  4. Obesity: identification assessment and management of overweight and obesity in children young people and adults; NICE Clinical Guideline (November 2014)

  5. Shedding the Pounds: Obesity Management, NICE Guidance and Bariatric Surgery in England; Office of Health Economics, 2012

  6. Caniano DA; Ethical issues in pediatric bariatric surgery. Semin Pediatr Surg. 2009 Aug18(3):186-192.

  7. Hsia DS, Fallon SC, Brandt ML; Adolescent bariatric surgery. Arch Pediatr Adolesc Med. 2012 Aug166(8):757-66. doi: 10.1001/archpediatrics.2012.1011.

  8. Picot J, Jones J, Colquitt JL, et al; Weight loss surgery for mild to moderate obesity: a systematic review and economic evaluation. Obes Surg. 2012 Sep22(9):1496-506. doi: 10.1007/s11695-012-0679-z.

  9. Varela JE, Wilson SE, Nguyen NT; Outcomes of bariatric surgery in the elderly. Am Surg. 2006 Oct72(10):865-9.

  10. Eldar SM, Heneghan HM, Brethauer SA, et al; Laparoscopic bariatric surgery for those with body mass index of 70-125 kg/m2. Surg Obes Relat Dis. 2012 Nov-Dec8(6):736-40. doi: 10.1016/j.soard.2011.09.024. Epub 2011 Oct 14.

  11. Guidelines for Clinical Application of Laparoscopic Bariatric Surgery; Society of American Gastrointestinal and Endoscopic Surgeons, 2008

  12. Pories WJ; Bariatric surgery: risks and rewards. J Clin Endocrinol Metab. 2008 Nov93(11 Suppl 1):S89-96. doi: 10.1210/jc.2008-1641.

  13. Arterburn DE, Courcoulas AP; Bariatric surgery for obesity and metabolic conditions in adults. BMJ. 2014 Aug 27349:g3961. doi: 10.1136/bmj.g3961.

  14. Nguyen NT, Nguyen B, Gebhart A, et al; Changes in the makeup of bariatric surgery: a national increase in use of laparoscopic sleeve gastrectomy. J Am Coll Surg. 2013 Feb216(2):252-7. doi: 10.1016/j.jamcollsurg.2012.10.003. Epub 2012 Nov 21.

  15. Familiari P, Boskoski I, Marchese M, et al; Endoscopic treatment of obesity. Expert Rev Gastroenterol Hepatol. 2011 Dec5(6):689-701. doi: 10.1586/egh.11.77.

  16. GP Guidance: Management of nutrition following bariatric surgery, The British Obesity and Metabolic surgery society (Aug 2014)

  17. Primary care management of postoperative bariatric surgery patients, The British Obesity and Metabolic Surgery Society (Sept 2014)

  18. Sjostrom L; Review of the key results from the Swedish Obese Subjects (SOS) trial - a prospective controlled intervention study of bariatric surgery. J Intern Med. 2013 Mar273(3):219-34. doi: 10.1111/joim.12012. Epub 2013 Feb 8.

  19. Tai CM, Huang CK, Hwang JC, et al; Improvement of nonalcoholic fatty liver disease after bariatric surgery in morbidly obese Chinese patients. Obes Surg. 2012 Jul22(7):1016-21. doi: 10.1007/s11695-011-0579-7.

  20. Kim JH, Wolfe B; Bariatric/metabolic surgery: short- and long-term safety. Curr Atheroscler Rep. 2012 Dec14(6):597-605. doi: 10.1007/s11883-012-0287-3.

  21. Stroh C, Birk D, Flade-Kuthe R, et al; Evidence of thromboembolism prophylaxis in bariatric surgery-results of a quality assurance trial in bariatric surgery in Germany from 2005 to 2007 and review of the literature. Obes Surg. 2009 Jul19(7):928-36. doi: 10.1007/s11695-009-9838-2. Epub 2009 May 5.

  22. Eid I, Birch DW, Sharma AM, et al; Complications associated with adjustable gastric banding for morbid obesity: a surgeon's guides. Can J Surg. 2011 Feb54(1):61-6.

  23. Desbeaux A, Hec F, Andrieux S, et al; Risk of biliary complications in bariatric surgery. J Visc Surg. 2010 Aug147(4):e217-20. doi: 10.1016/j.jviscsurg.2010.08.001.

  24. Odom J, Zalesin KC, Washington TL, et al; Behavioral Predictors of Weight Regain after Bariatric Surgery. Obes Surg. 2009 Jun 25.

  25. Peterhansel C, Petroff D, Klinitzke G, et al; Risk of completed suicide after bariatric surgery: a systematic review. Obes Rev. 2013 Jan 9. doi: 10.1111/obr.12014.