Types of Bariatric Surgery: UK Guide

Types of bariatric surgery vary in how they work, who they suit, and what risks they carry. In the UK, the main options include gastric bypass, sleeve gastrectomy, adjustable gastric band, one-anastomosis gastric bypass, and biliopancreatic diversion with duodenal switch. Each procedure works by restricting food intake, altering nutrient absorption, or both. NICE recognises bariatric surgery as clinically effective for eligible adults with severe obesity, and procedures are performed in specialist NHS and private centres. Understanding the differences between procedures, eligibility criteria, and long-term commitments is essential before making any decision.

What are the main types of bariatric surgery available in the UK?

The main types are gastric bypass, sleeve gastrectomy, adjustable gastric band, one-anastomosis gastric bypass, and biliopancreatic diversion with duodenal switch, all performed in specialist NHS and private centres across the UK.

The main types of bariatric surgery available in the UK are gastric bypass (Roux-en-Y), sleeve gastrectomy, adjustable gastric band, one-anastomosis gastric bypass (OAGB, sometimes called mini gastric bypass), and biliopancreatic diversion with duodenal switch (BPD/DS).^[1][6] These procedures are collectively referred to as bariatric or weight-loss surgery and are performed to help people with severe obesity achieve sustained weight reduction when other interventions have not been effective.

Each procedure works through a different mechanism: restricting the amount of food the stomach can hold, altering the way nutrients are absorbed, or a combination of both. NICE guidance recognises bariatric surgery as a clinically effective intervention for eligible adults with obesity, and procedures are carried out in specialist NHS and private centres across the UK.^[2][3] (The NICE guideline number applicable to surgical eligibility should be confirmed with your specialist team or via the NICE website, as guidance in this area has been updated in recent years.)

A less commonly performed option is the intragastric balloon, a non-surgical, endoscopic procedure. It is available privately in the UK, though NHS commissioning varies by Integrated Care Board (ICB) and it is generally considered a short-term adjunct rather than a definitive surgical treatment. The choice of procedure depends on individual clinical factors, including body mass index (BMI), comorbidities, and patient preference, and should always be made in discussion with a specialist multidisciplinary team.

How does each procedure work and who is it suitable for?

Procedures work through restriction, malabsorption, or both; suitability depends on BMI, comorbidities such as type 2 diabetes, and individual clinical factors assessed by a specialist multidisciplinary team.

Gastric bypass (Roux-en-Y) produces weight loss through both restriction and malabsorption: the surgeon creates a small stomach pouch and reroutes the small intestine so that food bypasses most of the stomach and the upper small bowel. It is generally considered particularly effective for people with type 2 diabetes or severe gastro-oesophageal reflux disease alongside obesity, in line with NICE and BOMSS guidance. NICE recommends considering surgery in adults with a BMI of 40 kg/m² or above, or 35 kg/m² or above with a significant obesity-related condition such as type 2 diabetes or hypertension.^[3][4]

Sleeve gastrectomy involves removing approximately 80 per cent of the stomach, leaving a narrow, sleeve-shaped tube. It restricts food intake and is associated with reductions in the hunger hormone ghrelin. It is suitable for a similar BMI range and is often preferred when the risks of a more complex procedure need to be minimised, though it may worsen gastro-oesophageal reflux in some patients.^[12][13]

OAGB (one-anastomosis gastric bypass) is an established procedure used in some UK centres. It creates a long, narrow stomach pouch and a single join to the small bowel, producing both restriction and a degree of malabsorption. Outcomes data are broadly comparable to Roux-en-Y bypass for weight loss and type 2 diabetes remission, and it is recognised by BOMSS as an option in appropriate patients.^[8][9]

The adjustable gastric band is a silicone band placed around the upper stomach to create a small pouch. It is the least invasive surgical option and is fully reversible, but it requires regular follow-up for band adjustments and tends to produce more modest weight loss than bypass or sleeve procedures. It is less commonly recommended as a first-line option in current UK practice.

BPD/DS is the most complex procedure, combining a sleeve gastrectomy with significant intestinal rerouting. It produces the greatest weight loss but carries the highest risk of nutritional deficiencies and is generally reserved for people with a very high BMI or specific metabolic conditions, in line with specialist centre guidance. All candidates should undergo thorough psychological and nutritional assessment before surgery.

People from certain ethnic backgrounds may be assessed at lower BMI thresholds, in line with NICE guidance recognising higher metabolic risk at lower BMIs in some populations, particularly in the context of type 2 diabetes.^[2][5]

Can I get bariatric surgery on the NHS, or do I need to go private?

NHS bariatric surgery is available for adults meeting NICE BMI criteria who have not achieved adequate weight loss through non-surgical means, though waiting times and commissioned procedures vary by Integrated Care Board.

Bariatric surgery is available on the NHS, but access depends on meeting specific clinical criteria and on local commissioning decisions made by Integrated Care Boards (ICBs). NICE guidance recommends that surgery should be considered for adults with a BMI of 40 kg/m² or above, or 35 kg/m² or above with a significant obesity-related condition such as type 2 diabetes or hypertension, provided that non-surgical interventions have been tried and have not achieved or maintained adequate weight loss.^[3][4]

In practice, NHS waiting times for bariatric surgery can be considerable, and not all ICBs commission every procedure type. Referral is typically made through a GP to a specialist tier 3 or tier 4 weight management service, where a multidisciplinary team will assess suitability.^[1] People from certain ethnic backgrounds may be assessed at lower BMI thresholds, in line with NICE guidance that recognises higher metabolic risk at lower BMIs in some populations, particularly in relation to type 2 diabetes.^[2][5]

For those who do not meet NHS criteria or who wish to explore other options, bariatric surgery is widely available privately in the UK. Private costs vary considerably depending on the procedure and the centre. It is important to verify that any private provider is regulated by the appropriate body for your location: the Care Quality Commission (CQC) in England, Healthcare Improvement Scotland, Healthcare Inspectorate Wales, or the Regulation and Quality Improvement Authority (RQIA) in Northern Ireland.

Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, for those exploring non-surgical options alongside or instead of surgery.

Regardless of whether surgery is pursued on the NHS or privately, long-term follow-up, including nutritional monitoring and psychological support, is an essential part of post-operative care.

What are the risks and side effects I should know about?

Risks include short-term surgical complications such as anastomotic leaks and blood clots, and longer-term issues including nutritional deficiencies, dumping syndrome, and weight regain if lifestyle changes are not maintained.

Bariatric surgery carries both short-term surgical risks and longer-term nutritional and physiological side effects that patients should understand before consenting to any procedure. In the immediate post-operative period, risks include bleeding, infection, blood clots (deep vein thrombosis and pulmonary embolism), anastomotic leaks (particularly after gastric bypass), and adverse reactions to anaesthesia. These risks are generally low in accredited specialist centres but are not negligible, and individual risk varies with age, BMI, and comorbidities.

Longer-term side effects depend on the procedure:

• Nutritional deficiencies are common after bypass, OAGB, and BPD/DS because of reduced absorption of iron, vitamin B12, calcium, and vitamin D. Lifelong supplementation and regular blood monitoring are required; your surgical team will advise on the specific regimen and monitoring schedule for your procedure, in line with BOMSS guidance.

• Dumping syndrome can occur after gastric bypass and OAGB, causing nausea, sweating, and diarrhoea after eating sugary or high-fat foods.^[15][20] Late dumping can also cause post-bariatric hypoglycaemia (low blood sugar), which may present as shakiness, sweating, or confusion some hours after eating.^[15] If you experience these symptoms, discuss them with your surgical team or GP.

• Reflux may worsen after sleeve gastrectomy in some patients.

• Band slippage or erosion is a recognised complication of adjustable gastric banding and may require further surgery.

• Weight regain is possible with all procedures if dietary and lifestyle changes are not maintained.

• Rapid weight loss after surgery increases the risk of gallstones. Some centres use ursodeoxycholic acid prophylaxis in the months following surgery; ask your team whether this applies to you, and report any upper abdominal pain or symptoms suggestive of biliary colic promptly.

Medication safety after bariatric surgery is important. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen should generally be avoided after gastric bypass and OAGB because of the risk of marginal ulcers.^[18][19] Modified-release and narrow-therapeutic-index medicines may be absorbed differently after surgery. Always inform your GP, pharmacist, and any other prescriber that you have had bariatric surgery so that your medicines can be reviewed.

Pregnancy and contraception: it is generally recommended to avoid pregnancy for at least 12 to 18 months after bariatric surgery, while weight is changing rapidly and nutritional status is being established.^[23][24] Malabsorptive procedures may reduce the effectiveness of oral contraceptives; discuss alternative contraceptive methods with your GP or surgical team before and after surgery.

Patients should contact their GP if they experience persistent vomiting, severe abdominal pain, signs of infection at the wound site, or symptoms suggestive of nutritional deficiency such as fatigue, numbness, or hair loss. For urgent concerns, NHS 111 can provide advice, and any life-threatening symptoms such as difficulty breathing or severe chest pain require an immediate call to 999.

Suspected side effects from any medicines used in the peri-operative period can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. Open communication with the surgical team and GP throughout recovery is essential for safe long-term outcomes.

Scientific References

1. What is weight loss surgery?.
2. Overweight and obesity management (NG246).
3. Overweight and obesity management (NG246) – Medicines and surgery chapter.
4. Obesity | Treatment summaries – BNF.
5. Overweight and obesity management (NG246) – Identifying and assessing overweight, obesity and central adiposity.
6. Single-anastomosis duodeno-ileal bypass with sleeve gastrectomy – overview (HTG423).
7. Plasma Ghrelin Levels after Diet-Induced Weight Loss or Gastric Bypass Surgery.
8. IFSO Update Position Statement on One Anastomosis Gastric Bypass (OAGB).
9. One-Anastomosis Versus Roux-en-Y Gastric Bypass in the Resolution of Comorbidities: A Non-inferiority Meta-analysis and Meta-regression.
10. A Comprehensive Review of Sleeve Gastrectomy, Roux-en-Y Gastric Bypass, One-Anastomosis Gastric Bypass, Duodenal Switch, and SADI-S: Very Long-Term Outcomes at 10 Years and Beyond.
11. One anastomosis gastric bypass (OAGB): a scoping review.
12. Laparoscopic Sleeve Gastrectomy Versus One-Anastomosis Gastric Bypass and the Risk of De Novo or Persistent Gastroesophageal Reflux Disease: A Systematic Review and Meta-Analysis.
13. Conversion to One-Anastomosis Gastric Bypass versus Roux-en-Y Gastric Bypass for Treatment of Gastroesophageal Reflux Disease after Sleeve Gastrectomy: A Systematic Review and Meta-analysis.
14. Ten-Year Follow-Up for Sleeve Gastrectomy Versus Roux-en-Y Gastric Bypass: A Systematic Review and Meta-Analysis.
15. Early and Late Complications After Sleeve Gastrectomy and Roux-en-Y Gastric Bypass: A Narrative Review.
16. The Nutritional Challenges Following Revisional Bariatric Surgery After Sleeve Gastrectomy: A Systematic Review and Meta Analysis.
17. Racial disparities in selected micronutrient deficiencies after bariatric surgery: A systematic review.
18. Nonsteroid anti-inflammatory drugs and the risk of peptic ulcer after Roux-en-Y gastric bypass.
19. Surgical Options for Refractory Anastomotic Ulcer after Roux-en-Y Gastric Bypass: A Narrative Review of the Literature.
20. More Anastomotic Ulcers, Less Dumping, and Equal Weight Loss in Long vs. Short Gastric Pouch in Laparoscopic Roux-en-Y Gastric Bypass.
21. Efficacy of prophylactic ursodeoxycholic acid in preventing gallstone formation after metabolic bariatric surgery: an updated systematic review and meta-analysis of randomized controlled trials.
22. Ursodeoxycholic Acid Prophylaxis and the Reduction of Gallstone Formation After Bariatric Surgery: An Updated Meta-Analysis of Randomized Controlled Trials.
23. Impact of Surgery-to-Conception Interval on Maternal and Perinatal Outcomes Following Laparoscopic Sleeve Gastrectomy: A Retrospective Cohort Study.
24. Pregnancy Outcomes After Metabolic Bariatric Surgery According to the Surgery-to-Conception Interval: A Multicentre Retrospective Cohort Study (MOMBARIS 2).

Frequently Asked Questions