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What is the most effective operation for adults with severe and complex obesity?

BMJ 2014; 348 doi: (Published 14 March 2014) Cite this as: BMJ 2014;348:g1763
  1. Jane M Blazeby, professor of surgery, honorary consultant surgeon12,
  2. James Byrne, consultant surgeon3,
  3. Richard Welbourn, consultant surgeon4
  1. 1Centre for Surgical Research, School of Social and Community Medicine, University of Bristol, Bristol BS8 2PR, UK
  2. 2Division of Surgery, Head and Neck, University Hospitals Bristol NHS Foundation Trust, Bristol
  3. 3Department of Upper Gastrointestinal Surgery, University Hospital Southampton NHS Trust, Southampton, UK
  4. 4Department of Upper Gastrointestinal and Bariatric Surgery, Musgrove Park Hospital, Taunton, UK
  1. Correspondence to: J M Blazeby j.m.blazeby{at}

Accessing, undergoing, and achieving a successful outcome from surgery for “severe and complex obesity” is difficult and requires determination and effort. Here, we consider “severe and complex obesity” to mean that an individual’s health is compromised by his or her weight to the extent that surgery can be considered to be an appropriate option.1 Surgery may be offered to adults with a body mass index (BMI) of ≥40, or a BMI of ≥35 with an obesity related disease, and it can be very successful. An average 50% of excess weight may be lost in the first few years after surgery, and if this is sustained it is associated with long term reduction in overall mortality and decreased incidences of diabetes, myocardial infarction, stroke and cancer.1 2 This treatment, however, requires careful consideration and serious commitment, with the need to demonstrate full engagement in a structured weight loss programme, to have tried all appropriate non-invasive measures of weight loss, and persevered for referral to a specialist surgical team.1 Once surgery is approved it is necessary to choose which operation to undergo.

Worldwide, three operations predominate: laparoscopic adjustable gastric band surgery (gastric band), laparoscopic Roux-en-Y gastric bypass (gastric bypass), and laparoscopic sleeve gastrectomy. In gastric band surgery an adjustable band is placed around the top of the stomach (fig 1). Gastric bypass, which takes longer to perform than a band and requires more operative skill, involves creation of a small gastric pouch that is attached to a limb of intestine so ingested food bypasses the duodenum and proximal small intestine (fig 2). In sleeve gastrectomy, which is technically less complex than a bypass, the greater curvature of the stomach is resected (fig 3).


Fig 1 Gastric band surgery showing (a) a small “virtual” pouch of stomach below the gastro-oesophageal junction and (b) gastro-gastro tunnelling sutures. (Reproduced from SM Griffin, SA Raimes, J Shenfine. Oesophagogastric Surgery. 5th ed. Saunders Elsevier, 2013)


Fig 2 Gastric bypass showing short vertical lesser curve-based gastric pouch with Roux-en-Y jejuno-jejunostomy reconstruction. (Reproduced from SM Griffin, SA Raimes, J Shenfine. Oesophagogastric Surgery. 5th ed. Saunders Elsevier, 2013)


Fig 3 Sleeve gastrectomy. (Reproduced from SM Griffin, SA Raimes, J Shenfine. Oesophagogastric Surgery. 5th ed. Saunders Elsevier, 2013)

All the procedures reduce eating capacity and influence appetite and satiety by changing the hormonal milieu and by possible vagal nerve feedback. The surgery itself also necessitates changes in eating and lifestyle behaviours, critical factors which maintain sustained weight loss and which require appropriate support in follow-up. Band surgery requires follow-up “band consultations” to regulate the gastric capacity by adjusting the volume of fluid in the band (a band fill or defill). After gastric bypass, long term vitamin supplementation and monitoring is needed—particularly of the fat soluble vitamins, folic acid, and zinc—to ensure a good outcome and to avoid potentially dangerous nutritional sequelae (such as bone demineralisation due to vitamin D deficiency).3 After all types of surgery, provision of dietary and lifestyle advice is important. Most patients are anatomically suitable for the three types of bariatric surgery.

Increasing numbers of procedures are being undertaken in many countries, although the prevalence of each is changing.4 5 In 2009-10, gastric band, gastric bypass, and sleeve gastrectomy accounted for 21%, 67%, and 10% of procedures in the UK National Health Service respectively, but more recent data for individual UK surgeons and worldwide surveys show that fewer gastric bands are being inserted and there is a dramatic increase in sleeve gastrectomy, with rates of the three procedures in the UK now being approximately 10%, 60%, and 25% respectively.4 5

What is the evidence of uncertainty?

Randomised controlled trials

A systematic review in 2009 included 20 randomised controlled trials examining the clinical and cost effectiveness of bariatric surgery.6 We updated this and identified five additional trials with searches in Medline and the Cochrane Libraries using search terms for bariatric surgery combined with terms for obesity and a validated filter for randomised controlled trials, restricted to studies in humans. Of the 25 trials, two compared gastric band and bypass,7 8 and three evaluated sleeve gastrectomy.9 10 11 The remainder focused on rare specialist interventions or historic procedures.

The trials of gastric band and bypass, while being landmark studies, included just 301 patients, were at a single centre, and were at high risk of bias.7 8 Allocation concealment was inadequate, subjects were excluded after randomisation, and there was no blinding of outcome assessors. One study assessed quality of life (QoL), but details of questionnaire response rates were missing.8 Although both trials showed a weight loss benefit for gastric bypass, their methodological weaknesses mean that results lack rigour and generalisability.

The three trials comparing types of sleeve gastrectomy with gastric band or bypass had similar methodological flaws.9 10 11 Those reporting outcomes at 12 and 36 months showed that, although surgery results in significant weight loss, there were no differences between procedural types.10 11 The systematic review concluded that well designed, long term trials comparing different operative techniques are required that include an assessment of quality of life and that a comparison of procedures such as gastric bypass with the restrictive procedures (particularly gastric band) is desirable.6 The review stated, however, that because of strong preferences held by surgeons and patients, such a trial would be impossible to do.

Registries and national audits

Evidence from national registries and large cohort studies including patients undergoing bariatric surgery is useful to consider rates of rare events such as in hospital death. The UK National Bariatric Surgery Registry (NBSR), the US Bariatric Outcomes Longitudinal Database (BOLD), and other registries show the safety of surgery (NBSR and BOLD reporting outcomes on 8710 and 57 918 operations respectively).5 12 13 In hospital mortality is about 0.1%. Gastric band and sleeve gastrectomy have consistently lower in hospital mortality than gastric bypass.

Long term outcome data in the registries are incomplete, however, meaning that rates of re-operation or weight regain for each type of surgery are unknown. Gastric bands may require minor “servicing,” major revision, or removal for slippage or erosion. After gastric bypass, surgery to treat internal hernia (where the bowel protrudes within a restricted space in the abdominal cavity and is at risk of incarceration) is occasionally required, and a small number of patients will experience life threatening problems associated with intestinal failure (inadequate digestion and absorption of nutrients to maintain energy, fluids, and micronutrient balance). A serious complication of sleeve gastrectomy is leakage from the gastric staple line, which may take months to heal.14

Which operation is optimal for patients with diabetes and other obesity related disease?

All operations can induce improvement or remission of type 2 diabetes. Although a widespread perception holds that gastric bypass is better than other types of bariatric surgery at improving diabetes remission and limiting progression of end organ damage, the lack of well designed clinical trials comparing different operations makes this difficult to ascertain.15 It is not known which operation most improves other obesity related disease, although it is widely assumed that sustained weight loss is the key to benefit.15

What is the impact of bariatric surgery on quality of life?

In general studies show that quality of life improves after surgery.16 It is difficult, however, to draw conclusions about differences between types of surgery in improved quality of life because of the confusing number of instruments used to measure quality of life and the lack of well designed comparative studies.17

Is ongoing research likely to provide relevant evidence?

The By-Band study is a large (724 patient), pragmatic, randomised controlled trial comparing the effects of gastric bypass versus gastric band on weight loss and quality of life at three years.18 The triallists and funding body will consider whether sleeve gastrectomy can also be evaluated as it expands into more centres. Searches in the WHO International Clinical Trials Registry identified ongoing trials comparing gastric bypass with sleeve gastrectomy, measuring weight loss, remission of obesity related disease, and quality of life, though some are small and single centred.19 20 21 22 The SurgiCal Obesity Treatment Study (SCOTS) is a longitudinal cohort study of 2000 patients having bariatric surgery in Scotland, who will be followed up for 10 years to determine outcomes including diabetic control, cardiovascular events, cancer incidence, quality of life, and cost.23

What should we do in light of the uncertainty?

There are some situations where one operation may legitimately be favoured. For example, severe gastro-oesophageal reflux would be regarded by many as a contraindication to sleeve gastrectomy, and if previous major bowel or abdominal wall surgery has been done or there is concurrent inflammatory bowel disease a gastric bypass may be precluded. Another consideration is the practicality of optimal follow-up of gastric band. Geographical difficulties may prohibit attendance, or the service may not be funded within the health system.

Aside from these concerns, it is critical for surgical teams and decision makers to understand what patients wish to achieve and expect from surgery. Although weight loss is easily measurable and a reasonable marker of outcome for the clinician, it is not necessarily the most important measure of success for the patient compared with improvement in obesity related disease or behaviour change. In most bariatric centres patients are given the choice of which operation to have, and provided with information. Information should highlight that no one operation will guarantee successful sustained weight loss and that behaviour change and a concerted effort from patients themselves are required. Ideally, all suitable patients should be encouraged to participate in well designed, multicentre, randomised controlled trials designed to answer questions about which surgery is best and most cost effective.

Recommendations for future research

  • The predominant need is to establish a culture of collaboration and active participation in randomised controlled trials in surgery24

  • Questions to be answered:

    • How does gastric band, gastric bypass, or sleeve gastrectomy affect weight loss, remission of obesity related disease, and overall quality of life five years after surgery?

    • Does gastric bypass or sleeve gastrectomy have lower rates of re-operation for complications and weight regain than gastric band surgery in the longer term (up to 10 years)?

    • Which outcomes of bariatric surgery are most important to patients and should be measured as a minimum in all studies?


Cite this as: BMJ 2014;348:g1763


  • This is one of a series of occasional articles that highlight areas of practice where management lacks convincing supporting evidence. The series adviser is David Tovey, editor in chief, the Cochrane Library. This paper is based on a research priority identified and commissioned by the National Institute for Health Research’s Health Technology Assessment programme on an important clinical uncertainty. To suggest a topic, please email us at

  • Contributors: The idea for this article was formulated by JMB in discussion with M Chew (associate editor, BMJ), RW, and JB. JMB wrote the first draft of the paper, and RW and JB commented on it. All authors approved the final version, and JMB is the guarantor.

  • Competing interests: We have read and understood the BMJ Group policy on declaration of interests, and we declare the following interests: JB has received travelling expenses to attend conferences from Ethicon and Covidien and consultancy fees to proctor procedures from GI Dynamics (Endobarrier), and is a co-investigator in the By-Band Study. RW has received contributions for travel, accommodation, conference fees, and consultancy fees for proctoring from Ethicon, Covidien, and Allergan; and is president of the British Obesity and Metabolic Surgery Society, chair of the National Bariatric Surgery Registry, and a co-investigator in the By-Band Study. JMB is chief investigator of the By-Band Study.

  • Provenance and peer review: Commissioned; externally peer reviewed.


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