How a gastric sleeve works
In a sleeve gastrectomy, around 75–80% of the stomach is removed keyhole, leaving a narrow tube about the size of a banana. The smaller stomach holds far less, so you feel full sooner.
Removing the part of the stomach that produces most of the hunger hormone ghrelin also reduces appetite for many patients. A sleeve is not reversible. See gastric sleeve for the full details.
How a gastric bypass works
In a Roux-en-Y gastric bypass, the surgeon creates a small stomach pouch and connects it directly to a lower part of the small intestine, bypassing most of the stomach and the first section of the intestine.
As well as limiting portions, a bypass changes gut hormones and how food is absorbed. It is particularly effective for type 2 diabetes and usually improves reflux. A mini gastric bypass (one-anastomosis) is a simpler variation. See gastric bypass and mini gastric bypass.
Sleeve vs bypass at a glance
| Gastric sleeve | Gastric bypass | |
|---|---|---|
| How it works | Makes the stomach smaller | Small pouch plus rerouted intestine |
| Operation time | 1–2 hours | 2–3 hours |
| Complexity | Technically simpler | More complex |
| Typical excess weight loss | 60–70% | 65–80% |
| Reflux / heartburn | May start or worsen | Often improves |
| Type 2 diabetes | Improves for many | Often the stronger effect |
| Vitamins | Lifelong supplements | Lifelong supplements, closer monitoring |
| Reversible | No | Technically possible, rarely done |
| Istanbul package | £2,900–£3,800 | £3,400–£4,300 |
| Private UK price | £8,700–£13,500 | £10,000–£15,500 |
Am I eligible for weight-loss surgery?
Check your BMI and see which options our bariatric team would usually consider.
International guidelines from the American Society for Metabolic and Bariatric Surgery (ASMBS) and IFSO recommend surgery for people with a BMI of 35 or more, and suggest considering it from a BMI of 30 for people with metabolic disease such as type 2 diabetes. In the UK, NICE guidance uses similar thresholds alongside other criteria.
Gastric Sleeve: 7 nights in Istanbul
- Before you travel
You complete a medical questionnaire and send recent blood results. A bariatric surgeon and a dietitian review them, confirm you meet the criteria, and you receive a written fixed quote. You start the two-week pre-operative liver-shrinking diet at home.
- Day 1Arrival
Your driver meets you at Istanbul airport and takes you to the hotel. Rest after the flight.
- Day 2Assessment
Blood tests, ECG, chest X-ray, abdominal ultrasound and an endoscopy, followed by consultations with your surgeon, the anaesthetist and the dietitian. You are admitted to hospital in the evening.
- Day 3Surgery
The operation takes one to two hours. You wake in your room, and you will be asked to stand and walk the same evening — this matters more than it sounds, because walking is what prevents blood clots.
- Day 4Leak test and first liquids
A swallow test confirms the staple line is sealed, after which you begin sips of water and clear liquids.
- Day 5Discharge
You move to the hotel, walking regularly and managing your liquid diet with your coordinator checking in daily.
- Days 6 and 7Recovery in the hotel
Light activity. Your coordinator is on WhatsApp at any hour, and the hospital is fifteen minutes away if anything concerns you.
- Day 8Final check and fly home
Bloods repeated, your surgeon confirms you are fit to fly, and you leave with your discharge summary, medication, supplements and a written diet plan.
- After you are home
Dietitian appointments at 2 weeks, 1, 3, 6 and 12 months, with your surgeon available throughout.
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How to choose
- Significant reflux or heartburn? A bypass is usually preferred, because a sleeve can make reflux worse.
- Type 2 diabetes? Both help, and a bypass often has the stronger effect on blood sugar.
- Concerned about lifelong absorption issues? A sleeve has simpler long-term nutritional needs.
- Very high BMI? Some surgeons favour a bypass or a staged approach; your surgeon will explain.
- Previous stomach surgery? This can change the options; tell your surgeon early.
The final decision should be made with a bariatric surgeon after reviewing your history, blood tests and, often, an endoscopy.
The trip to Istanbul
Both operations follow a similar plan: around seven nights in Istanbul, with three nights in hospital and four in a hotel, so your surgeon can check you through the first days. Before you travel, you follow a two-week liver-shrinking diet, which makes keyhole surgery safer.
The day-by-day plan for the sleeve is shown above. A bypass trip is almost identical.
Risks to be aware of
- Both operations: bleeding, infection, leaks from the staple line, blood clots and gallstones.
- Gastric sleeve: new or worsening reflux and heartburn.
- Gastric bypass: vitamin and mineral deficiencies, dumping syndrome, ulcers (especially with smoking or anti-inflammatory painkillers) and small bowel problems.
Serious complications are uncommon in experienced hands. Choose a hospital with intensive care on site and a surgeon who performs these operations every week.
Life after surgery
- Liquids (about 2 weeks): clear fluids and protein drinks in small sips.
- Purée (about 2 weeks): smooth, blended, protein-rich foods.
- Soft foods (about 2–4 weeks): foods that are easy to mash with a fork.
- Normal textures: small, balanced meals, eaten slowly and chewed well.
Long term, you will eat much smaller portions, prioritise protein, take vitamins every day and have regular blood tests. Twelve months of dietitian support is included in a good package, and you should also register with your GP for long-term monitoring.
Non-surgical alternatives
Surgery is not the only option, and for some people it is not the first step.
| Option | How it works | Typical use |
|---|---|---|
| Gastric balloon | A balloon in the stomach for 6–12 months | Lower BMI, or as a first step |
| Gastric Botox | Injections that slow stomach emptying | Modest weight loss without surgery |
| Weight-loss medication | Prescribed injections that reduce appetite | Discuss with your GP or specialist |
| Surgery (sleeve, bypass) | Permanent change to the stomach and gut | BMI 35+, or 30+ with metabolic disease |
Non-surgical options usually produce less weight loss than surgery and can be harder to maintain. They can still be the right start, depending on your health and goals.
What long-term success looks like
Surgery is a powerful tool, not a cure. The people who keep their weight off long term have a few things in common:
- They attend follow-up appointments and have regular blood tests.
- They take their vitamins every day, for life.
- They eat protein first, in small portions, and avoid drinking with meals.
- They build regular activity into daily life.
- They ask for help early if old habits return, rather than waiting.
Frequently asked questions
On average a bypass leads to slightly more weight loss than a sleeve, but the difference is modest. Long-term success depends mostly on eating habits and follow-up.
Yes. If severe reflux develops or weight is regained, a sleeve can usually be converted to a bypass.
Most patients fly home after around seven nights, once the surgeon has checked them and they are drinking comfortably.
Some people have loose skin after major weight loss. Body contouring, such as a tummy tuck, is usually considered once your weight has been stable for six to twelve months.
