Gastric Bypass

Gastric Bypass: Surgery, Risks, Side Effects & Results

Gastric sleeve

The laparoscopic sleeve gastrectomy is a restrictive procedure that involves removing the majority of the stomach, turning the stomach into a thin tube-like structure, thus reducing the capacity of your stomach to approximately 50 mL initially and later to approximately 100 mL.

Weight loss with the sleeve gastrectomy is faster than with the gastric band and weight loss of 60 to 70% of excess body weight can be achieved by 12 months.

The safety profile of the sleeve gastrectomy lies between the gastric band, which is the safest, and the laparoscopic gastric bypass.

Like the gastric band, the sleeve gastrectomy works as a restrictive procedure. Your anatomy is not altered and therefore there is less requirement for you to take any vitamin supplements.

Unlike the gastric bypass, your stomach is still accessible by endoscope and you can continue to take oral medications and eat any food. However there is not as much long term data with the sleeve gastrectomy as the other two procedures and there is some suggestion that there can be some weight gain at ten years.

Please carefully weigh up the advantages and disadvantages of each bariatric procedure before you decide which one is your procedure of choice. Where appropriate your surgeon will make a recommendation of which procedure you should consider as being the most appropriate for your medical condition.

How is a gastric bypass performed?

The gastric bypass procedure involves making several small incisions through which laparoscopic instruments are inserted to perform the surgery.

The procedure is designed to make a small reservoir or pouch for food at the upper end of your stomach with the capacity of about 30 mL.

This pouch is connected to the small intestine by a new anastomosis, or join. The outlet of this join is about 4 cm in diameter. Ingested food therefore bypasses the majority of your stomach which remains alive and undisturbed in the abdominal cavity.

Put another way, the majority of your stomach does not have food passing through it. As a result there is an associated prolonged decrease in appetite and sometimes even a temporary aversion to food.

This procedure is predominantly a restrictive procedure and achieves weight loss by limiting the amount of food or liquid that can be taken at any time.

There is a small aspect of malabsorption which requires you to take vitamins and supplements for the rest of your life. The procedure results in rapid weight loss initially which stabilises over a 12 to 18 month period.

Pre-gastric bypass surgery preparation and precautions


If you are a woman you should avoid pregnancy in the first year postoperatively. Periods of rapid weight loss are not the right time to be trying to get pregnant or trying to maintain an existing pregnancy.

Also bear in mind that as you lose weight your fertility will increase and you are more likely to become pregnant. Female gastric banding patients can and do get pregnant and with appropriate support from obstetricians, will have an uneventful pregnancy.

Obviously it is important should you get pregnant, that you bring to your obstetricians attention as soon as possible the fact that you have had gastric bypass surgery.

Pre-surgery fasting

To make your surgery technically as safe as possible your surgeon may start you on an Optifast diet for at least two weeks prior to surgery.

This is designed to shrink your liver and reduce your risk of surgical complications. It also introduces you to the liquid dietary regime you will have in the postoperative period.

If your liver is excessively large at the time of surgery, your procedure may be aborted and rescheduled for a later date.


Smoking is a serious problem for bariatric surgical patients. It increases your risk of pulmonary complication and blood clots regardless of the procedure you have performed. It is strongly recommended that if you are a smoker, that you try and stop smoking prior to surgery.

Even stopping smoking a week before surgery can be of benefit.

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