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Gastric bypass surgery

3-minute read

Gastric bypass is a surgical procedure that can help people with obesity to lose weight and improve their health. It decreases the size of the stomach and changes the way the stomach and small intestine absorb food, making it easier to lose weight.

When should I consider gastric bypass surgery?

If you are very obese and have other health problems, and have tried hard to lose weight by dieting and doing more exercise, your doctor might suggest gastric bypass surgery to help with weight loss.

Gastric bypass surgery is the most effective type of surgery for weight loss, but it is not for everyone. Discuss with your doctor which approach is best for you, and talk about what to expect. You could ask:

  • What's the average loss of weight after a year?
  • What's the average loss of weight after 5 years?
  • What's my role after surgery?

Losing weight after gastric bypass surgery can help reduce problems with type 2 diabetes, asthma episodes and blood pressure, and can help improve heart health.

How do I prepare for gastric bypass surgery?

You are likely to need different tests to make sure that a gastric bypass is right for you.

Your doctor will advise you about any changes you need to make to medicines and diet in the weeks or days before surgery.

What happens during gastric bypass surgery?

Gastric bypass surgery is performed while you are under general anaesthetic and will probably involve a hospital stay of 3 to 5 days.

The surgery is usually done as a keyhole procedure, but sometimes an open operation is needed.

During the procedure, staples are used to create a small pouch in the top part of your stomach, as the image below shows.

The pouch is attached by stitches to the lower part of your small intestine so food that you eat will bypass most of the stomach and the first part of the small intestine.

Less food will be absorbed into the body and you will feel full after eating only a small amount.

illustration of a gastric bypass
The normal digestive system, and the digestive system after a gastric bypass.

What can I expect after the procedure?

At first, you'll be on liquid food only. That will change to pureed food then to solids after a few weeks.

A dietitian will advise you on how you can change your eating habits after gastric bypass surgery to keep healthy while losing weight.

You will also need to take vitamin and mineral supplements for life to replace those normally absorbed in the first part of the small intestine.

You have an important role to play - if you follow your dietary guidelines and do more physical activity, that will increase the amount of weight you will lose.

What can go wrong?

As with any surgery, there is a risk of infection or that the surgery doesn't work. There might also be bleeding or leaks from the staple line or joins, or bowel obstruction.

Some people find they have low blood sugar after surgery and feel weak. A few don't absorb all the nutrients they need. Talk to your doctor about the risks of the procedure.

More information

Visit our guide to bariatric surgery to learn more about the different types of bariatric procedure.

Also, be sure to ask your doctor any questions you might have about gastric bypass surgery.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: January 2019

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