Their call comes after new World Health Organisation (WHO) research showed that Australia is the only country in the world where childhood obesity is climbing faster than among adults. The number of overweight and obese children has doubled since 1985, and now affects 23 per cent of all those under the age of 16.

Professor Ian Caterson from Sydney University and Paul Zimmet from Monash University say prices on healthy foods must be cut to encourage better diets.

"Over the last few years, the things we want people to eat have gone up in price more than processed food," Professor Caterson told AAP.

"So if we make them cheaper, we're rewarding people for eating the right things rather than punishing them for eating the wrong things."

Although the two experts support calls by US-based WHO researcher Professor Barry Popkin to institute a so-called calorie tax on manufacturers to lift the price of unhealthy food, they suggest that subsidising fresh food could be more effective.

According to Professor Caterson, although eating habits are largely ingrained, research has proved that price affects what people buy. He pointed to one study showing that halving the price of apples boosted sales three-fold.

He suggested that government subsidies offered to growers, transporters or supermarkets could bring the price of fresh produce into line with processed foods.

The experts will discuss Australia's childhood obesity epidemic at the International Congress on Obesity in Sydney next month.

The use of 'traffic light' coloured labelling that helps consumers easily identify health or unhealthy foods could also go on trial in Australia.

The labeling, which gives a red light to high levels of salt, fat and sugar, an amber light to medium levels and a green light to low levels, has already been introduced in British supermarkets.

Fay Jenkins, the director of food policy and programs in the South Australian Health Department, told The Australian newspaper this week that the system should also be introduced in Australia.