How does the One Anastomosis Gastric Bypass work?

A small pouch is created from the stomach and connected directly to the small intestine via a single anastomosis. This reduces both the amount of food you can eat and the calories your body absorbs, while also reducing hunger and promoting early satiety.

How long is the hospital stay and recovery?

Most patients return home within 2–3 days. Return to normal activity is variable but typically takes around 3 weeks. The procedure itself takes 60–90 minutes under general anaesthesia.

How much does OAGB cost?

For patients with private health insurance covering weight loss surgery, the out of pocket cost is from $7,000. This includes initial consultation, pre-operative assessments, surgeon and assistant surgeon fees, dietitian and psychologist consultations, and comprehensive aftercare.

What conditions can OAGB improve?

OAGB can improve or resolve obesity-related conditions including type 2 diabetes, high blood pressure, and sleep apnoea. These improvements often begin within weeks of surgery.

What are the short-term complications of OAGB?

Possible short-term complications include bleeding, infection at incision sites, leakage at the surgical join (anastomosis), blood clots, and nausea or vomiting during the adjustment phase. These are typically managed promptly with medical or surgical intervention if needed.

What are the long-term complications of OAGB?

While rare, long-term complications can include bile reflux, nutrient deficiencies (especially iron, vitamin B12, calcium, and vitamin D), dumping syndrome, ulcer formation, and weight regain if lifestyle changes are not maintained. Lifelong follow-up with regular blood tests is essential.

Is OAGB right for me?

OAGB may be a strong option if you have a BMI over 35, or over 30 with related health issues, want a technically simpler procedure than the traditional Roux-en-Y gastric bypass, are committed to long-term lifestyle changes, and are seeking significant and lasting weight loss.

Where can I get an OAGB consultation in Melbourne?

Our experienced surgeons can discuss OAGB or other weight loss surgery with you at our Dandenong North, Berwick, Frankston, Warragul or Cranbourne locations.

One Anastomosis Gastric Bypass (OAGB)

Q: How much weight can I lose with OAGB?

OAGB typically results in 65–80% excess weight loss within 12–18 months. It is a powerful option for those looking for a permanent solution to obesity, especially if previous attempts at weight loss have not been successful.

Summary:

One anastomosis gastric bypass (OAGB), or mini gastric bypass, joins a small stomach pouch directly to the small intestine, so you eat less and absorb fewer calories. It is usually done by keyhole surgery. You are supported by our multidisciplinary team of surgeons, a Specialist GP, dietitians, a psychologist and an exercise professional, with lifelong follow up. It is from $7,000 with private health insurance covering weight loss surgery. Our Melbourne surgeons are based in Dandenong North, with consulting rooms in Berwick, Frankston, Cranbourne and Warragul.

One Anastomosis Gastric Bypass Surgery

The One Anastomosis Gastric Bypass (OAGB), also known as the Mini Gastric Bypass, is a modern, effective weight loss surgery that combines restriction and malabsorption to help you lose weight and keep it off long-term.

During the procedure, a small pouch is created from the stomach and connected directly to the small intestine — reducing both the amount of food you can eat and the calories your body absorbs. The surgery typically takes about 60–90 minutes and is performed under general anaesthesia, often via keyhole (laparoscopic) technique for faster recovery.

By changing the digestive pathway, this procedure can help reduce hunger, promote early satiety, and even improve or resolve obesity-related conditions such as type 2 diabetes, high blood pressure, and sleep apnoea.

Most patients return home within 2-3 days and begin seeing results within weeks. It's a powerful option for those looking for a permanent solution to obesity, especially if previous attempts at weight loss haven't been successful.

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One Anastomosis Gastric Bypass OAGB diagram showing stomach pouch and intestinal connection

Most commonly performed type of bypass surgery in some Australian bariatric centres
Typically results in 65–80% excess weight loss within 12–18 months
Can improve or resolve conditions like type 2 diabetes, hypertension, and sleep apnoea
Performed laparoscopically (keyhole surgery) in the majority of cases
Average hospital stay: 2-3 days
Return to normal activity: This can be variable but some take 3 weeks
OAGB is covered by many private health insurers, with item number 31575 under the MBS (if eligible)

When comparing costs, please be aware that our costs include all of the following:

Initial consultation with Surgeon
Pre-operative assessment with Specialist Physician
Clinical Psychologist consultation
Dietitian consultations inclusive of 1x pre-operative, 3x post-operative appointments
Exercise professional appointment
Surgeon and Assistant Surgeon
Access to on-call Surgeon at all times
Comprehensive after care at Medicare rebate

Our operations are performed only in Private Hospitals. These costs can vary according to your particular private health cover. It may be possible to fund this out of pocket cost from your Superannuation.

Possible Complications After Surgery (Short-Term)

While most patients recover smoothly, some may experience early complications, including:

Bleeding
Infection at incision sites
Leakage at the surgical join (anastomosis)
Blood clots (deep vein thrombosis or pulmonary embolism)
Nausea or vomiting, especially during the adjustment phase

These are typically managed promptly with medical or surgical intervention if needed.

Long-Term Complications (Months or Years Later)

While rare, some complications may occur well after surgery:

Bile reflux – stomach bile flowing into the oesophagus, causing discomfort
Nutrient deficiencies – especially in iron, vitamin B12, calcium, and vitamin D
Dumping syndrome – a rapid shift of food into the small bowel causing nausea, diarrhoea, or dizziness
Ulcer formation at the site of the bypass
Weight regain – particularly if lifestyle changes aren't maintained

Lifelong follow-up, including regular blood tests and nutritional support, is essential to reduce the risk of long-term issues.

The following are the commonest of the complications but please note that this is not a comprehensive list of possible complications but does cover most events.

The Risk of the Anaesthetic

Anaesthetic risks are extremely low because when you come to your operation any conditions which might increase your anaesthetic risk such as high blood pressure, diabetes or sleep apnoea will have been brought under control. All of our anaesthetists are experienced with dealing with the specific problems of patients with excess weight and have full access to all of the tests and information gathered during your preoperative assessment.

Bleeding

Although uncommon, bleeding can occur during an otherwise routine operation and could require blood transfusion and possibly abandoning the laparoscopic (keyhole) approach for a major incision in the abdomen. Occasionally, after a routine operation, bleeding can commence some hours after an operation and require a return to the operating theatre.

Infections

Again these are uncommon with laparoscopic surgery, but occasionally one of the small keyhole wounds can become infected and require antibiotics or drainage. Uncommonly, an infection inside the abdominal cavity or the chest can occur.

Damage to Other Organs

Although uncommon, during laparoscopic surgery it is possible to inadvertently damage another organ such as the spleen or the bowel. Normally this can be diagnosed and repaired during the operation but very rarely this damage may not be obvious until some hours or even days after the procedure and will then require appropriate management.

Conversion to Open Operation

Rarely, it is not possible to complete an operation with keyhole surgery and a full abdominal incision may be necessary. This is more likely to be the case if you have had previous surgery on your stomach such as a gastric band or stomach stapling.

Blood Clots to the Legs or Lung (Pulmonary Embolus)

Blood clots to the legs or the lungs are a very serious complication. At LapSurgery we use the maximum protection against this occurring. Shortly before the operation you will be given a blood thinning injection and have stockings placed on your legs. A further device will also be placed on your legs which keeps pumping blood through your legs whilst you're asleep to minimise the chance of a clot forming whilst you are on the operating table.

Using these precautions and the early mobilisation after the surgery that is possible with the keyhole operation, these complications have been uncommon in our patients.

The team at LAPSurgery Australia are recognised for their exceptional and major contribution to the Government sponsored Bariatric Safety Registry (BSR). The BSR tracks surgical complications and provides an unbiased safety record for weight loss surgery.