WA health officials are introducing stricter restrictions on publicly funded weight-loss surgery after a surge in demand saw the number of operations rise 44 per cent in a year.
Bariatric surgery such as lap-banding was once funded almost solely by private health insurance or the patient, but the number of people having free surgery in public hospitals has swelled.
They now make up a quarter of all weight-loss operations in WA. In 2010-11, 713 West Australians had Government-funded surgery, compared with 496 the previous year.
The public hospital cost of each weight loss surgery was estimated at more than $10,000 by the Australian Institute of Health and Welfare two years ago.
The Health Department is writing to doctors with details of new "standardised criteria" for patients to be eligible for the surgery because it says there is no clear policy across WA public hospitals.
With more than a quarter of Australian adults obese, there are concerns doctors are inappropriately referring people at the lower end of the scale instead of only the morbidly obese.
It could also be medically unsafe to operate on some very obese patients.
The department warns that some patients are likely to fall outside the new rules and will instead be referred for help from dietitians and counsellors.
Those already on the waitlist will not be affected.
Under the policy based on NSW guidelines, patients need to be aged 16 to 55 and have a body mass index of 40 or over, which means a man of average height needs to weigh 125kg or more.
People with a BMI of 35 or over will qualify only if they have an obesity-related condition such as type 2 diabetes or sleep apnoea.
But patients will also need to have tried to lose weight through diet and exercise and had psychological testing to prove they can make changes needed after surgery.
There are concerns some see it as a quick fix and still try to eat big amounts of food or kilojoule-rich items such as chocolate.
The rules say if patients cannot lose weight in 12 months using conventional measures, they are unlikely to be able to comply with advice after surgery to lose the necessary weight in the long term.
A department spokeswoman confirmed morbidly obese patients would need to meet safety criteria before having bariatric surgery in the public health system.
"Bariatric surgery is an option of last resort for morbidly obese individuals," she said.