Some of these diets helped her drop 16 kilograms at a time, but they never worked in the long term. By the time she was 26, Ms Irvine weighed 140 kilograms. To her embarrassment, she was so big she had to book two seats on a flight for fear she would not fit into one.

"It was definitely affecting what I could do," she says, adding that her weight put her at high risk of type 2 diabetes among other illnesses.

Frustrated yet determined to reverse her problem, Ms Irvine investigated gastric band surgery. Knowing it could cost thousands of dollars in a private hospital, she tried The Alfred – one of few public hospitals to offer the procedure at no cost to the patient.

After waiting five years, Ms Irvine finally got her operation in 2013. She was 160 kilograms at the time and now weighs 94 kilograms. The disability services worker is still losing weight and says the procedure has dramatically improved her life. She has even taken up softball – a sport she used to play as a child but gave up because of her weight.

"I wish I made the decision earlier," says the 35-year-old. "I have a lot more confidence now."

Ms Irvine is one of 1453 people whose experience of weight loss surgery was studied at The Alfred between 2007 and 2014. The research, published in the Australia and New Zealand Journal of Surgery, found that most of these people lost substantial amounts of weight and experienced improvements in their health as a result.

Participants had to have a body mass index over 35 with at least one associated health problem such as high blood pressure, but on average they were "super obese", meaning they had a BMI over 50. One patient had a BMI over 100 (the equivalent of four healthy people's weight).

Eighty-two per cent of patients said they would definitely or probably have the surgery again if given the choice. Ten per cent said they definitely would not or probably would not do it again, if given the choice, and 8 per cent were undecided.

The head of the upper gastrointestinal surgery unit at the hospital, Associate Professor Peter Nottle, said the study showed taxpayers should be comfortable funding weight loss surgery for "super obese" people who are very unlikely to lose weight in other ways and cannot afford to pay for the procedure in the private hospital system.

It also proved that a "high volume" weight loss surgery clinic operating on 300 people a year was viable for a public hospital, which can train junior surgeons, he said.

While the surgery carries risks, including infections, major blood loss and gastric reflux, Professor Nottle said these risks had to be weighed against the risks of doing nothing.

"This sort of weight is life threatening," he said. "Having a BMI over 60, even in young people, can mean you die suddenly."

Despite mounting research backing the procedure for such people, Professor Nottle said there was still stigma in the community and among doctors about it being a "quick fix" that is somehow not as legitimate as other surgical procedures.

Professor Wendy Brown, a surgeon and researcher at Monash University who also worked on the study, said the research produced excellent outcomes and showed the public hospital system could benefit from these procedures, too, because many participants would require frequent hospital care for diseases associated with their weight if they did not receive the intervention.

Some of the authors involved had received funding from companies that make weight loss surgery devices.

A spokesman for the Victorian Department of Health and Human Services said the government had funded The Alfred, the Austin and Western District Health services to perform weight loss surgery in recent years. The three services received $2.2 million in this year's budget for the procedures.