The operation in detail

How is the gastric bypass procedure done?

The gastric bypass is a weight loss surgery procedure. It is usually done in one of two ways, the traditional ‘Roux en Y’ bypass and the ‘Mini’ (or ‘Loop’) bypass. On this page we deal with the Roux bypass as this accounts for the vast majority of cases. You can read more about the mini bypass here.

The bypass is done laparoscopically (keyhole) and under general anaesthetic. You can expect to be in theatre for between 60 and 90 minutes only assuming your procedure is uncomplicated. You will then normally have 2 days and nights in hospital during which time we can observe you and make sure you are on track to full recovery.

The Roux en Y gastric bypass is generally regarded as the premier weight loss surgery procedure as it combines excellent weight loss with significant health benefits. It has also been established for over 30 years, so we have lots of long-term data to show it delivers great results for the long term as well as the short.

After the gastric bypass operation

 The simplest way to describe it is to say that the stomach and bowel are ‘re-plumbed’ so that the food you eat goes into a reduced stomach before passing directly into the bowel a little further down the bowel than was the case before.

The bypass works in two ways. Firstly, by reducing the size of the stomach and so restricting the amount of food that can be eaten. We usually reduce the stomach’s capacity by as much as 90-95%.

The other way it works is by changing the balance of hormones in the gut. It is this change in hormones, including GLP1, PYY and neurotensin that is linked to a reduction in appetite and to changes in appetite.  It is also the reason for the significant health benefits that diabetic patients experience immediately after surgery.

There was a view for many years that the bypass helped patients lose weight by reducing absorption of calories but although this happens the effect is only short-lived. the malabsorption of micronutrients continues for the long term however and bypass patients will need to take vitamin and mineral supplementation for the rest of their lives.

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