One Anastomosis Gastric Bypass (OAGB)

One Anastomosis Gastric Bypass (OAGB)

One Anastomosis Gastric Bypass (OAGB)


The One Anastomosis Gastric Bypass (OAGB) is also known as the ‘mini’, ‘single loop’, ‘single anastomosis’ or ‘omega loop’ gastric bypass and it is used to help treat obesity and obesity-related health problems.

The effect of an OAGB operation is that your body absorbs less of the available energy from your food, and it will also cause you to feel full after consuming smaller portions. Gastric bypass can be considered when diet and exercise are not effective in reducing weight, or when you have health problems due to your weight.

The OAGB operation is a tool for weight loss. Long-term success is dependent on a person committing significant lifestyle changes. With healthy changes, a person can expect sustained, long-term weight loss of approximately 30 to 35 percent of their total body weight.


You may be a suitable candidate for weight loss surgery if your body mass index (BMI) is over 30 and you have weight-related health problems or if your BMI is over 35 without any obesity-related conditions.

At your initial appointment, Dr Moar will meet with you to better understand your health and future goals and discuss treatment options with you.

Preoperative Instructions

Most people need to go on a very low-calorie diet (VLCD) in the weeks leading up to the surgery. Losing weight before surgery reduces the size of your liver and helps make the surgery safer.


OAGB is a keyhole procedure that involves creating a long, thin stomach pouch by stapling off a larger stomach section. A loop of small bowel is then attached to the gastric pouch.

The larger portion of the stomach and a length (typically 150 centimetres) of the small intestine is bypassed in the digestion of food.

People who wish to undergo a gastric bypass procedure must be committed to a long-term investment in their health. This includes taking multivitamin supplements (to compensate for nutrients that will be lost in a bypass procedure) and having regular blood tests to look for nutritional deficiencies.

Dr Moar will collaborate with you, your dietician, and your GP to formulate an individualised plan.

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