What is Gastric Bypass surgery?Bypass-401

The gastric bypass procedure involves creating a very small pouch out of the stomach and attaching it directly to the small intestine, bypassing most of the stomach and the first part of the small bowel. This small stomach pouch cannot hold large amounts of food, and by skipping the first part of the small bowel, hormones that control our appetite and food absorption are also affected. Together, this results in significant and sustained weight loss. This additional hormonal effect makes it a particularly effective operation for diabetes and other metabolic complications of obesity.

Why would I need this procedure?

Gastric bypass is considered by many surgeons to be the ‘gold standard’ operation for morbid obesity and is commonly done worldwide. It is the operation with which all other weight loss procedures are compared. This procedure has grown in popularity because it produces sustainable long-term weight loss in most patients, and reduces the risk of death from obesity. Many obesity-related conditions, such as type II diabetes, obstructive sleep apnoea, joint pain from arthritis, high cholesterol and high blood pressure, are either completely resolved or substantially improved.

Most patients achieve good to excellent weight loss results following gastric bypass surgery; typically this is 65-85% per cent of excess weight. Patients lose most of their excess weight in the first year and can lose more weight over the next six to 12 months. Weight will usually stabilise after this. There can be some weight regain, but this is usually minor. There is no amount of weight loss that is guaranteed.

How do I prepare for this surgery?

Please contact your specialist at least five days before the test if you are:
  • Taking blood thinners/anticoagulants i.e. Warfarin, Clopidogrel (Plavix), Dabigatran (Pradaxa), Enoxaparin (Clexane), Ticagrelor (Brilinta)
  • Taking Lithium medication
  • Diabetic
  • Pregnant
  • Suffering with a heart, lung or bleeding condition including having a pacemaker, heart valve disease or replacement
  • Suffering with kidney disease
You can continue all other medication as usual including Aspirin, unless you are told not to by your specialist. You should tell your specialist if you need to take antibiotics before dental treatment. If you do, you may also need to take antibiotics before this procedure.

2-3 weeks before surgery you commence the OPTIFAST diet, a very low-calorie diet (VLCD) that is <800kcal per day that completely replaces your meals/ diet (Nutritionally complete).

Hospital staff will contact you and obtain your personal health history and may call you to clarify any information.

You will also be contacted by the customer service team to give you fasting instructions, time of arrival and to finalise payment arrangements.

If you smoke, you should attempt to restrict this for at least two weeks prior to surgery.

Try to increase your physical exercise for at least 2 weeks before surgery as well to help you be in the best condition for your procedure.

What happens during surgery?

Gastric bypass is now routinely done by laparoscopic (keyhole) surgery, which involves several very small incisions, rather than by open surgery, which uses one large incision. Harmless CO2 gas is introduced into the abdomen, inflating it, and creating a space for the surgeon to work. The surgeon introduces a long narrow camera and surgical instruments to perform the procedure. Laparoscopic procedures have the advantages of less pain and shorter hospital stay and recovery, as well as significantly reduced risks of wound infection or hernias. If, for some reason, your surgeon cannot complete the procedure laparoscopically, he can switch safely to the open procedure. The chance of this happening is low and would only be done in your best interests.

Gastric bypass is a more technically challenging procedure to perform than other surgical procedures available but for most people recovery time and risk is similar to the sleeve gastrectomy (also known as the gastric sleeve).

How long will I need to stay at the hospital?


Usually patients recover after a two night stay and are ready to go home. After surgery, patients start on liquids before moving to a pureed diet while the stomach heals.

For more information on what to expect before and after your procedure, please click on the links below.

Below are the Specialists Who You Can Book for this Procedure

Mr Barnaby Smith

Mr Barnaby Smith

General, Bariatric and Endoscopic Surgeon


Barnaby Smith is a general, laparoscopic and endoscopic surgeon with sub-specialist interest in upper gastrointestinal conditions, melanoma, laparoscopy, and hernia repairs. He prefers to use minimally invasive techniques such as laparoscopy to improve the outcome for his patients.

Mr Robert Cable

Mr Robert Cable

General, Laparoscopic and Obesity Surgeon

MBChB (Otago), FRCS (England), FRACS
Rob is a General and Bariatric Surgeon with expertise in Laparoscopic surgery. His Bariatric Surgery involves mainly Sleeve Gastrectomy, but also has proficiency in administering Lap Bands.