Gastric Sleeve Surgery: How It Works, the Risks, and the Results
Key takeaways
- A sleeve gastrectomy removes about 70 to 80% of the stomach, leaving a narrow sleeve that holds far less and lowers the hunger hormone ghrelin.
- It is done by keyhole surgery, takes about 1 to 2 hours, and usually means a 1 to 2 night hospital stay.
- Most people lose around 60 to 70% of their excess weight over 12 to 18 months, with many seeing type 2 diabetes and other conditions improve.
- It is major, irreversible surgery with real risks, including reflux, and works only alongside lifelong changes to how you eat.
A gastric sleeve (sleeve gastrectomy) is an operation that removes about 70 to 80% of the stomach, leaving a narrow, banana-shaped sleeve that holds far less food and reduces the hunger hormone ghrelin. It is one of the most common weight-loss operations in the world. This is the main guide; the decision, the cost, and recovery each have their own deeper article.
I had mine in my forties after years of dieting, and the single most useful thing was understanding exactly what the surgery does and does not do before I committed. Here is that picture.
What a gastric sleeve is
The surgeon removes the larger, curved part of your stomach and staples the rest into a slim tube, or sleeve. Your stomach goes from holding roughly a litre or more to holding a small fraction of that. Nothing is rerouted, which makes the sleeve simpler than a gastric bypass, and there is no implant or band left inside you.
How it helps you lose weight
The sleeve works two ways at once:
- Restriction: the small sleeve fills quickly, so you feel full after a little food.
- Hormones: the removed part of the stomach made most of your ghrelin, the main hunger signal, so appetite usually falls as well.
That combination is why many people find it easier to eat less than willpower alone ever allowed. It is still a tool, not magic: results come from pairing it with lasting changes to how you eat.
Who it is for
Surgery is generally considered at a BMI of 40 or above, or 35 or above with an obesity-related condition such as type 2 diabetes, high blood pressure, or sleep apnoea; updated guidance lowers those thresholds further for people with metabolic disease. Whether it is right for you is an individual decision made with a specialist team. Our guide to whether you are a candidate covers the criteria in full.
The operation
The sleeve is done laparoscopically (keyhole), through a few small cuts, and takes about 1 to 2 hours. Most people stay in hospital 1 to 2 nights. You will be up and walking the same day, partly to lower the risk of blood clots.
The risks
The sleeve is generally safe, but it is major surgery. The main risks are:
- A staple-line leak (about 1% or under), the most serious early complication
- Bleeding, blood clots (VTE), and narrowing (stricture) of the sleeve
- Reflux (heartburn), which the sleeve can cause or worsen, sometimes enough to need treatment or, rarely, conversion to a bypass
- Long term: vitamin and mineral deficiencies, so lifelong supplements and monitoring are essential
Mortality is low, around 0.1 to 0.3%, but the surgery is irreversible and should never be taken lightly.
The results
Most people lose around 60 to 70% of their excess weight over 12 to 18 months, and many see type 2 diabetes, blood pressure, and sleep apnoea improve or resolve. The weight loss is fastest in the first six months and then settles. Keeping it off is the real work, and it depends far more on the new habits than on the operation itself.
If you are weighing it up, read on about who the sleeve is for, what it costs, and what recovery is really like.
This guide is general information, not a diagnosis or a recommendation. Decisions about surgery should be made with a qualified bariatric team who can assess you individually.
References
- Weight loss surgery, NHS.
- Sleeve gastrectomy, Mayo Clinic.
- Bariatric Surgery Procedures, American Society for Metabolic and Bariatric Surgery (ASMBS).
Frequently asked questions
How does a gastric sleeve make you lose weight?
In two ways. Removing most of the stomach leaves a small sleeve that physically holds much less food, so you feel full sooner. It also removes the part of the stomach that produces most of your ghrelin, the main hunger hormone, so appetite usually drops too. Together that makes it easier to eat less, but the surgery is a tool, not a cure: long-term results depend on changing how you eat for good.
Is gastric sleeve surgery safe?
For most suitable patients it is considered safe, and the risk of dying is low, roughly 0.1 to 0.3%. But it is major surgery with real risks, including a staple-line leak (about 1% or under), bleeding, blood clots, narrowing of the sleeve, and reflux. Your surgical team will weigh these against the risks of staying at your current weight, which can be considerable.
How much weight will I lose with a gastric sleeve?
Most people lose about 60 to 70% of their excess weight over 12 to 18 months, though it varies a lot with your starting point, your health, and how closely you follow the plan. I lost most of mine in the first year, but the people who keep it off are the ones who treat the surgery as the start of a new way of eating, not the finish line.
Can a gastric sleeve be reversed?
No. Unlike a gastric band, the sleeve cannot be reversed, because the removed part of the stomach is gone for good. In some cases it can be converted to a gastric bypass later, for example if reflux becomes a serious problem or weight comes back, but you should treat the sleeve as a permanent change.
How long does it take to recover from a gastric sleeve?
Most people are back to desk work in about 2 to 4 weeks and avoid heavy lifting for 4 to 6 weeks, with a staged diet from liquids to solids over roughly 6 to 8 weeks. Full physical recovery takes a couple of months, but adjusting to the new way of eating takes longer.
Written by Claire Maddox. Medically reviewed by Mr Ian Calloway, MBBS, FRCS.
Our guides are written from personal experience and reviewed by a qualified clinician for accuracy. Read our editorial policy.