Roux-en-Y gastric bypass surgery

With this surgery, your surgeon connects a small part of your stomach directly to a part of your small intestine so that food bypasses most of your stomach and the top part of your small intestine.

Roux-en-Y gastric bypass is considered the gold standard of weight loss surgery.

How it works

  1. The part of your stomach that remains functional is significantly smaller so you should feel full sooner, and eat less.
  2. Because you have less functioning stomach and a shorter small intestine, your gut is able to absorb fewer calories and nutrients.
  3. Rerouting the food stream changes your gut hormones, which can make you feel full, suppress hunger, and reduce or even reverse type 2 diabetes.

How the surgery is done

After you’ve been put to sleep with general anaesthetic, your surgeon makes small incisions in your abdomen and reduces the size of your stomach down to a small pouch with a volume of approximately 30 millilitres (the size of a walnut – normal stomach volume is 1 litre).

Next, the surgeon detaches the first part of your small intestine, and attaches the bottom end of the detached small intestine to the newly created stomach pouch.

The final step in the procedure is attaching the top part of the detached small intestine to the small intestine further down. This is done so that stomach acids and digestive enzymes from your bypassed stomach and the functioning part of your small intestine will eventually mix with your food.

The surgery takes between 2 and 3 hours. Average time off work is 4 to 6 weeks.


  • it produces significant long-term weight loss (up to 80% of excess weight)
  • it can improves glucose control in type 2 diabetes and can help control high cholesterol, sleep apnoea and high blood pressure
  • it restricts the amount of food that you can eat in one go
  • it may lead to an increased metabolic rate which encourages weight loss
  • it changes your gut hormones to reduce your appetite and make you feel full
  • Most people can maintain  more than 50% excess weight loss.


  • the surgery isn’t easily reversible
  • technically it’s a more complex surgery than a gastric band or sleeve
  • there are complications in 10% of surgeries
  • complications can include leaks in the gut (up to 5%), bleeding (1%), infection, blood clots, lung or breathing problems
  • it can result in long-term vitamin and/or mineral deficiencies particularly vitamin B12, iron, calcium and folate
  • you need to stick to dietary recommendations, life-long vitamin/mineral supplementation, and have regular follow-up appointments
  • you'll be in hospital for longer than gastric band surgery
  • common adverse effects after recovery include gallstones (22% – 71%), diarrhoea (24%), ulcers (4%), hernia (3% – 16%), stricture where the parts of your gut are joined together (5% – 16%), bowel obstruction (1%), nausea, vomiting, low blood sugar, malnutrition and stomach perforation.  


Information is provided by HCF in good faith for the convenience of members. It is not an endorsement or recommendation of any form of treatment nor is it a substitute for medical advice, and you should rely on the advice of your treating doctors in relation to all matters concerning your health. Every effort has been taken to ensure the accuracy of the information, however HCF takes no responsibility for any injury, loss, damage or other consequences of the use of this information.