Key Takeaways
- Gastric sleeve removes around 80% of the stomach; gastric bypass creates a small pouch and reroutes the intestine. Both are performed laparoscopically.
- The sleeve typically achieves 60–70% excess weight loss and the bypass 70–80% — both within 18–24 months.
- Bypass is often preferred for BMI 40+, type 2 diabetes or severe acid reflux; the sleeve suits patients who want a simpler operation with fewer long-term supplements.
- NHS waiting times average 22–34 months; in Turkey, surgery can usually be scheduled within 2–4 weeks at 60–70% lower cost.
In this guide: How each works Side-by-side comparison Which is right for you NHS vs Turkey FAQ
Gastric sleeve or gastric bypass? It is one of the most common questions UK patients ask when they consider bariatric surgery. Both operations deliver significant, lasting weight loss — but they work differently, carry different risks and suit different patients.
At NewMe Health Clinic in Antalya, bariatric surgery is performed by Op. Dr. Mani Habibi (IFSO member, Cleveland Clinic trained, 4,500+ weight loss procedures) and Prof. Dr. Nurullah Bülbüller. In this guide we compare what you need to know — weight loss, recovery, costs, NHS eligibility and which operation suits which patient.
How gastric sleeve and gastric bypass work
Gastric sleeve (sleeve gastrectomy)
A gastric sleeve permanently removes around 80% of the stomach, leaving a narrow, banana-shaped “sleeve”. This sharply reduces how much you can eat at one sitting. Removing the upper part of the stomach (the fundus) also removes most of the cells that produce ghrelin, the hunger hormone — most patients feel noticeably less hungry after surgery.
The operation takes 45–60 minutes through 4–5 small incisions. It does not change the route food takes through the intestine, so nutrient absorption stays largely normal. The sleeve is the most commonly performed bariatric operation worldwide, according to IFSO.
Gastric bypass (Roux-en-Y)
A gastric bypass creates a small, egg-sized stomach pouch (around 30 ml) and reroutes the small intestine so that food bypasses part of the upper gut. This combination — restriction plus mild malabsorption — makes it the most powerful of the standard bariatric operations for weight loss and metabolic health.
At NewMe the operation takes about 2–3 hours, laparoscopically. Because food bypasses part of the small intestine, lifelong vitamin and mineral supplements are needed (B12, iron, calcium, vitamin D and a multivitamin). Bypass is often considered the reference operation for severe obesity with type 2 diabetes, because of its strong effect on blood sugar control.
Gastric sleeve vs gastric bypass: side-by-side comparison
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| Feature | Gastric sleeve | Gastric bypass |
|---|---|---|
| How it works | Removes around 80% of the stomach | Small pouch + intestinal rerouting |
| Operation time | 45–60 minutes | About 2–3 hours |
| Excess weight loss | 60–70% in 18–24 months | 70–80% in 18–24 months |
| Type 2 diabetes | Often improves or goes into remission | Strongest effect of the standard operations |
| Typical BMI range | 30–45 | 35–60+ |
| Hospital stay | 3–4 nights | 2–3 nights |
| Time in Antalya | About 7 days | 6–7 days |
| Back to desk work | About 2 weeks | 10–14 days |
| Reversible? | No (permanent) | Technically reversible (rarely done) |
| Vitamin supplements | Recommended (daily multivitamin) | Essential for life (B12, iron, calcium, D) |
| Acid reflux | Can worsen reflux (GORD) | Often improves or resolves GORD |
| Dumping syndrome | Very rare | Possible with sugary food — manageable |
| UK private cost | £9,000–£12,000 | £10,000–£15,000 |
| Turkey (NewMe) | Typically 65–75% less — see prices | Typically 65–75% less — see prices |
Which procedure is right for you?
A gastric sleeve may suit you better if you…
- Have a BMI between 30 and 45
- Want a simpler, shorter operation
- Don’t have severe acid reflux or Barrett’s oesophagus
- Prefer lighter long-term vitamin requirements
- Are having weight loss surgery for the first time
- Want steady weight loss over 18–24 months
A gastric bypass may suit you better if you…
- Have a BMI of 40 or above (or 35+ with significant obesity-related conditions)
- Have poorly controlled type 2 diabetes
- Suffer from severe acid reflux (GORD)
- Have had weight loss surgery before that didn’t deliver results
- Need the strongest weight loss effect
- Are ready to commit to lifelong vitamin supplements
Not sure? Your surgeon recommends the operation after reviewing your BMI, medical history, reflux symptoms and goals at your free assessment — and will tell you honestly if a balloon or a non-surgical route fits you better.
NHS vs Turkey: access and waiting times
On the NHS, the journey from GP referral to bariatric surgery typically takes 22–34 months:
- GP consultation to specialist referral: 2–4 months
- Mandatory Tier 3 weight management programme: 6–12 months
- Bariatric clinic assessment to approval: 2–4 months
- Surgical waiting list: 6–18 months (varies by region)
NHS eligibility requires a BMI of 40+, or 35+ with a significant obesity-related condition (NICE guideline CG189). For the full breakdown, read our guide to NHS weight loss surgery waiting times.
At NewMe Health Clinic in Turkey, surgery can usually be scheduled within 2–4 weeks of your first consultation, with no mandatory pre-surgery programme and more flexible BMI criteria (BMI 30+ for a sleeve, 35+ for a bypass). Packages cover the operation, hospital stay, transfers and aftercare, with hotel nights booked separately — at around 65–75% less than published UK private prices.
What our UK patients say
“This clinic changed my life. I’ve been 3 times — 2020 gastric sleeve, 2024 gastric bypass, 2025 360 tummy tuck and arm lift. I’ve successfully lost 15 stone, all thanks to this clinic and their amazing team.”
— Verified UK patient, Trustpilot review
“I had a gastric sleeve at NewMe in December 2021. I lost 8 stone in the first 9 months and have maintained my weight ever since. I’m now a healthy size 10/12 from a size 22.”
— Verified UK patient, Wupdoc review
Individual results vary.
Frequently asked questions
Can I switch from a gastric sleeve to a gastric bypass later?
Yes. This is called revisional bariatric surgery. If a sleeve doesn’t deliver enough weight loss, or you develop acid reflux, your surgeon can convert it to a bypass. Revision cases are assessed individually — see our gastric bypass guide.
Which procedure has a lower complication rate?
The gastric sleeve generally has a slightly lower overall complication rate than the bypass, mainly because it is a simpler operation that doesn’t involve rerouting the intestine. Both have low complication rates when performed by experienced teams. At NewMe, both operations are performed by IFSO-member bariatric surgeons at Temos-accredited Anatolia Hospital, and your surgeon explains your personal risk before you book. See the NHS overview of weight loss surgery for the general risks.
Will I regain weight after either surgery?
Weight regain is possible after both operations if diet and lifestyle changes aren’t maintained. The bypass may have a slightly lower long-term regain rate because of its hormonal and malabsorptive effects, but the biggest factor in long-term success is commitment to diet, exercise and follow-up — not the specific procedure.
How soon can I fly home to the UK after surgery?
Most patients fly home about 7 days after a gastric sleeve and 6–7 days after a gastric bypass, once their surgeon has given fit-to-fly clearance at the final check. The flight from Antalya to most UK airports takes about 4 hours.
Do I need to take vitamins for life after a gastric sleeve?
After a sleeve, a daily multivitamin is recommended, and deficiencies are less common than after a bypass. After a bypass, lifelong B12, iron, calcium, vitamin D and a multivitamin are essential because nutrient absorption is reduced. Your NewMe dietitian gives you a personal supplement plan before you fly home.
Medically reviewed by Op. Dr. Mani Habibi
Bariatric Surgeon · IFSO Member · Cleveland Clinic trained · Co-Founder, NewMe Health Clinic · View profile
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