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During this surgery, the surgeon creates a pouch similar in size to an egg therefore restricting the volume that can be eaten.

However, this pouch is detached from the main part of the stomach. The lower part of the small bowel is then cut, moved up to and attached to the pouch.

The bowel that has been bypassed is then attached to the small bowel, thereby allowing the digestive juices from the pancreas to be mixed with the food coming from the small pouch.


The bypass works in two ways:

It restricts the amount that can be eaten and the by-passing of some of the small bowel means that there is a reduction in the amount of calories, protein, vitamins and minerals absorbed.

To try to prevent vitamin and mineral deficiencies, you will be required to take a daily vitamin and mineral supplement for life.

You will be expected to have regular blood tests to ensure nutritional adequacy, which may require further supplements such as iron, calcium, Vitamin D, Zinc etc.


What are the Benefits and Drawbacks of having a Bypass?


  • You can expect to lose 60 - 70% of your excess body weight after 2 years
  • Average initial weight loss is quick
  • Evidence suggests that gut hormones can be altered which affects appetite
  • Has a high-resolution rate of diabetes (75%)



  • Has a higher mortality rate (1;250 chance) and more serious complications than other operations
  • It will be necessary to take multivitamin and minerals for life. You may need to take extra supplements based on your dietary intake and blood tests
  • ‘Dumping syndrome’ can occur after eating foods with too much sugar or fat, with symptoms including; nausea, sweating, faintness, vomiting and potentially diarrhoea
  • It is effectively irreversible. For example, if it were deemed an medical emergency, it could be reversed
  • Medication needs to be reviewed to ensure adequate absorption
  • You may not lose or maintain weight loss if you do not stick to healthy eating and lifestyle guidelines
  • It is recommended you avoid alcohol for 1 year after surgery. It may be limited after this, as the side effects of alcohol can occur more rapidly after the bypass


Please note: Lifelong vitamin and mineral supplements are expected with both the Gastric Bypass and the Sleeve Gastrectomy and you will need regular bloods tests to monitor your nutritional status