Short answer: Both operations can produce substantial weight loss. In SLEEVEPASS, Roux-en-Y bypass had greater median excess weight loss and less oesophagitis at ten years; Oseberg found higher five-year diabetes remission after bypass in its participants with type 2 diabetes. Sleeve preserves the normal intestinal route. Neither procedure is right for everyone: your surgeon should assess reflux, diabetes, nutritional risks, medications and preferences before recommending one. Dr Murat Üstün offers both procedures.
Sleeve vs Bypass at a Glance
| Factor | Gastric sleeve (LSG / VSG) | Roux-en-Y gastric bypass (RYGB) |
|---|---|---|
| How it works | Part of the stomach is removed; the intestine is not rerouted. | A small stomach pouch is connected to the small intestine, bypassing part of the upper digestive tract. |
| Weight at 5 years | 61.1% excess BMI loss (SM-BOSS) | 68.3% excess BMI loss (SM-BOSS); difference not statistically significant after adjustment |
| Weight at 10 years | 43.5% median excess weight loss (SLEEVEPASS) | 50.7% median excess weight loss (SLEEVEPASS) |
| Type 2 diabetes remission at 5 years | 20%, HbA1c ≤6.0% (Oseberg) | 50%, HbA1c ≤6.0% (Oseberg) |
| Reflux | Symptoms worsened in 31.8% at 5 years (SM-BOSS); oesophagitis in 31% at 10 years (SLEEVEPASS) | Symptoms worsened in 6.3% and resolved in 60.4% at 5 years (SM-BOSS); oesophagitis in 7% at 10 years (SLEEVEPASS) |
| Reoperations or interventions by 5 years | 15.8% (SM-BOSS) | 22.1% (SM-BOSS) |
| Aftercare | Lifelong nutritional follow-up and supplements as advised | Lifelong nutritional follow-up and supplements; deficiency risk can be greater |
| Later options | Conversion to bypass may be considered for persistent reflux or regain | Revision options depend on anatomy and the cause of symptoms or regain |
| IBC price | £2,450 Ultra Eco (sleeve-only at a partner hospital) · £4,550 Relaxation · £4,900 Luxury | £5,000 Relaxation · £5,350 Luxury |
Sources: SM-BOSS (JAMA, 2018); SLEEVEPASS (JAMA Surgery, 2022); Oseberg five-year analysis (Lancet Diabetes & Endocrinology, 2025). These are different studies and populations; five-year excess BMI loss is not the same metric as ten-year excess weight loss. Individual results vary.
How Each Operation Works
A gastric sleeve removes part of the stomach to create a narrow tube. Food continues through the normal intestinal route; the removed stomach cannot be replaced. Hunger signalling can change, but responses vary.
A Roux-en-Y gastric bypass creates a small stomach pouch and reroutes food into the small intestine. It changes absorption and gut hormones and can improve reflux and blood-glucose control, but it also creates distinct nutritional and surgical risks.
When Might Sleeve Be Considered?
- No significant reflux after assessment
- A preference to retain the normal intestinal route
- Medication absorption or other clinical factors favouring a non-bypass option
A sleeve can cause or worsen reflux. Your surgeon should review symptoms, investigations and longer-term aftercare before deciding.
When Might Roux-en-Y Bypass Be Considered?
- Significant reflux or oesophagitis after specialist evaluation
- Type 2 diabetes where the potential metabolic benefit matters
- A willingness and ability to maintain lifelong supplements and follow-up
Bypass is not automatically preferable for every person with reflux, diabetes or a particular BMI. Individual risks, previous surgery and treatment goals matter.
What About the Mini Gastric Bypass?
One-anastomosis (mini) gastric bypass is a separate operation. Read the sleeve vs mini bypass comparison or the mini gastric bypass guide rather than treating the Roux-en-Y evidence above as mini-bypass evidence.
How Dr Üstün Decides
Dr Murat Üstün reviews your history, reflux symptoms, diabetes, medication, prior operations and other relevant test results before recommending a procedure. Learn about Dr Murat Üstün. A personalised consultation is essential; trial averages are not a prediction of your outcome.
For pricing and what each tier includes, see the sleeve price guide and bariatric surgery cost guide. The £2,450 Ultra Eco tier is sleeve-only at a partner hospital, not an all-inclusive package. Confirm your written quote and deposit terms before paying.
Gastric Sleeve vs Gastric Bypass — Frequently Asked Questions
Which is better, gastric sleeve or gastric bypass?
Neither is better for everyone. Trial results favour Roux-en-Y bypass for some outcomes, particularly reflux, but the choice depends on your health, medicines and surgical assessment. The SM-BOSS five-year difference in excess BMI loss was not statistically significant after adjustment.
Which loses more weight?
At five years, SM-BOSS reported 68.3% excess BMI loss after bypass versus 61.1% after sleeve; this difference was not statistically significant after adjustment for multiple comparisons. At ten years, SLEEVEPASS reported median excess weight loss of 50.7% versus 43.5%, respectively. Excess BMI loss and excess weight loss are different measures, not directly comparable.
Is gastric bypass better for type 2 diabetes?
For participants with obesity and type 2 diabetes in the Oseberg trial, 50% after bypass versus 20% after sleeve met the trial's HbA1c ≤6.0% remission criterion at five years. This does not guarantee remission for an individual; SLEEVEPASS did not find a statistically significant difference in diabetes remission at ten years.
Should I avoid a sleeve if I have acid reflux?
Significant reflux merits a careful discussion with your bariatric surgeon. In SM-BOSS, reflux symptoms worsened in 31.8% after sleeve and 6.3% after bypass; reflux resolved in 60.4% after bypass. Your symptoms, endoscopy findings and other risks determine the appropriate operation.
Can a sleeve be converted to a bypass later?
Conversion to Roux-en-Y bypass may be considered for persistent reflux or weight regain after sleeve, subject to specialist assessment. Revision surgery has its own risks and is not a guaranteed solution.
How much do sleeve and bypass cost in Turkey?
At Istanbul Bariatric Center, sleeve is £2,450 Ultra Eco (sleeve-only at a partner hospital), £4,550 Relaxation or £4,900 Luxury. Roux-en-Y bypass is £5,000 Relaxation or £5,350 Luxury. Relaxation and Luxury are performed by Dr Üstün at JCI-accredited Liv Hospital Vadistanbul. Confirm what your individual quote includes before booking.
For revision options, see revision bariatric surgery in Turkey.