People with private health insurance are nine times more likely than those without to have bariatric weight-loss surgery, a new study has found.

Bariatric surgery, which includes gastric banding, sleeve gastrectomy and gastric bypass surgery, involves reducing the amount of food the stomach can hold and is seen as effective in treating obesity where exercise and diet changes have failed. The most common type of surgery performed in Australia is lap band surgery.

It is usually only recommended for people with a body mass index over 40kg/m2 or those with a body mass index over 35 kg/m2 and obesity-related conditions such as diabetes.

The new study, published in the Medical Journal of Australia, looked at hospital data for 49,364 obese people and found that people with an annual household income of $70,000 or more were five times more likely to undergo surgery than those who earned less than $20,000 a year.

The data was drawn from the Sax Institute’s 45 and Up Study.

Medicare covers bariatric surgery in public hospitals but only a relatively small number of bariatric procedures are performed in public hospitals. People who elect to be treated as a public patient in a private hospital will have some of the cost subsidised by Medicare, but will have to pay for medicines and pricey hospital accommodation fees.

“Hence, the surgery is largely taken up by those who have private health insurance and who can afford what are often large associated out-of-pocket costs,” said the study’s lead author, Dr Rosemary Korda from The Australian National University’s National Centre for Epidemiology and Population Health.

“While resources issues may limit access to bariatric surgery, we need to have an important national conversation about distributing them more fairly,” said Dr Korda.

“Although we have ‘universal’ health care in Australia, there are system-wide issues relating to how the health system is structured and funded – including the mix of public and private care, cost-sharing between state and federal governments, limited resources and out-of-pocket expenses – that underlie some of the inequality in health care.”

While some see bariatric surgery as a complex, risky alternative to diet and exercise, Dr Korda said it may be the only solution for some people with severe obesity.

“For many people, simple exercise and diet changes do not result in a sustained weight loss, often despite years of trying,” she said.

“While this surgery is not risk free, there is clear evidence that it is very effective in treating people with severe obesity — not only does it result in substantial weight loss, it leads to improvements in obesity-related health conditions such as diabetes and joint disease.”

Wendy Brown, Director of Monash University’s Centre for Obesity Research and Education said the study highlighted a failure of state and federal governments to tackle obesity treatment.

“Prevention would be the ideal, but the fact is that over 2.5 million adults in Australia are obese now, and they need treatment, just like any other disease. Currently, the only durably effective treatment for obesity is bariatric surgery,” she said.

Dr Brown, who was not involved in the study, also urged governments to accept the cost effectiveness of bariatric surgery, pointing out that a recent study found the cost-benefit to society was equivalent to the cost-benefit from ceasing smoking.

Dr Brown also called for the creation of a national register for bariatric surgery so trends in its uptake, success and risks could be more accurately monitored.