Research from Canberra University's Health Research Institute found one in four Australian children were overweight, although this number could be halved with simple changes.

The research, conducted with Robert de Castella's charity SmartStart for Kids, was based on data collected from a sample of 31,000 Australia students since 2000. It found the prevalence of obesity could be reduced markedly within 15 months.

"We asked what it would take to reverse the increase seen in the prevalence of overweight in Australian school children over recent decades," said professor of public health Tom Cochrane.

"We were surprised by the answer: just a small daily dietary restriction equivalent to just one treat-size bar of chocolate and about 15 minutes extra of moderate physical activity per day."

"Overweight and obesity is widespread in Australian school children," the report said. "No class, school or community in our sample was immune."

The report found advertising and exposure to junk food were obstacles to reform along with limited access to healthy, affordable foods in schools.

"Clearly, this is a societal problem related to the way that children's lives are lived today compared with the way they would have been lived 40 years ago, when the so-called problem of childhood obesity did not exist at the epidemic levels seen today."

Mr de Castella said childhood obesity was causing significant health challenges and required renewed attention.

"Each day kids are exposed to a series of factors which affect their weight, such as the availability and exposure to food and drink; loss of opportunities for play; and the uptake of television and other media which encourage sedentary lifestyles," Mr de Castella said.

"However, this research demonstrates that child obesity can be addressed and throws down a challenge for Australia to do better for its children and their future health and wellbeing."