Melbourne obesity expert John Dixon says between one and two per cent of Australians - up to 400,000 people - are severely obese and very ill with weight-related conditions, but not getting the help they need.
"It is widely acknowledged now that it's too late to help these people through diet and exercise changes, but the one thing we know that works, obesity surgery, they're not getting," said Professor Dixon, head of obesity research at the School of Primary Healthcare at Monash University.
"Today that group of people is being completely neglected and that is totally irresponsible."
Laparoscopic banding, in which a band is surgically wrapped around the stomach to limit food capacity, accounts for 95 per cent obesity surgery in Australia, but the procedure is mostly limited to private hospitals.
About 10 per cent of Australians are severely obese, with a body mass index (BMI) over 35, making them eligible for surgery, but there is a sub-group who are "dangerously" in need of it, said Prof Dixon, president of the Australian and New Zealand Obesity Society.
"These are people who are very, very ill indeed with diabetes and other problems and are in and out of hospital constantly, placing a lot of strain on the health system," he said.
"They deserve easier access to the one treatment we know works and saves lives, we know that, yet we're sitting on our hands."
In the journal Obesity Surgery, Prof Dixon said surgery should be the standard care for all people with a BMI over 50, the super-morbidly obese, and those with a BMI over 40 with other related conditions.
Bariatric surgery should also be routinely discussed as an option for other obese people, he said.
"Currently this is all optional, but we need to get smart about this and change how we're doing things."
Professor Paul Zimmet, director of the International Diabetes Institute in Melbourne, agreed the patients most in need of obesity surgery were missing out, largely because they were on lower incomes and could not afford private care.
"It's good news that state governments are investigating getting surgery into the public system," Prof Zimmet said.
"But the worry will be in making sure it is only made available to those patients who really need it, who can't lose their weight by other, less invasive means."
