Australian Associated Press

New star rating food labels are based on outdated research and won't tackle Australia's expanding waistline, a nutrition expert says.

The new labelling system, announced by federal health minister Tanya Plibersek in June, aims to help Australians choose healthier meals by rating foods on their fat, sugar and salt content.

But a nutritionist says the five-star ratings are based on outmoded research that ignores current science's more holistic understanding of nutrition and places too much emphasis on energy content.

"The rating stars ignore the two new components of food — protein and low GI content," said Professor Jennie Brand-Miller of the University of Sydney's School of Molecular Bioscience.

"For example, breast milk would have two red marks, one for saturated fat and one for sugar."

Speaking at a food labelling conference in Sydney on Wednesday, Prof Brand-Miller said she was "very, very uncomfortable" with a star system which was underpinned by outdated research.

"The energy content of the food is not the best way to judge (it) — lentils and liquorice have the same energy density," she said.

The best way to stop Australians moving up their belt buckles is to encourage people to get on the scales twice a week and not rely on government-imposed labels to keep them slim, she said.

However, the star rating system has received support from the Public Health Association of Australia.

PHAA CEO Michael Moore says while the information presented with the star system may not meet the standards of "academic rigour", it would help ordinary Australians make better diet choices.

He said the star system was built from the best information available at the time but would be open to regular updates as new scientific findings arose.

The federal government launched the star rating system last month, in a bid to lower rates of chronic disease and weight problems in Australia.

Nearly half of the national population currently qualifies as overweight, with four million considered obese.