23/01/2017 10:41 AM AEDT | Updated 23/01/2017 2:11 PM AEDT

Preschool Obesity Is A $17 Million Problem In Australia, And It's Getting Worse

Before kids start school, 1 in 5 are overweight and 1 in 20 are obese.

The cost of having an obese preschooler will set a family back a few hundred dollars a year, but it's costing the nation more than $17 million.

The study, published in the Australian and New Zealand Journal of Public Health, calculated the direct healthcare cost of obesity for children aged two to four, including the fact they're twice as likely to go to hospital for treatment, as well as GP appointments and emergency visits.

The Centre of Research Excellence in the Early Prevention of Obesity in Childhood research found the annual direct cost to the Australian healthcare system was $17 million, and the cost to families was $367 a year compared to a healthy weight child.

How big is the problem?

About 20 percent of children are already overweight or obese by the time they start school; and five percent of Australian children aged 2–4 years are classified with obesity.

Research fellow Vicki Brown told The Huffington Post Australia the $17 million tag didn't include ongoing costs as children aged.

"We know that obesity in childhood is associated with poor health outcomes and higher health costs in adulthood," Brown told HuffPost Australia.

"This research also suggests there are significant immediate benefits if we intervene to prevent obesity as well as those longer-term benefits."

The research is part of a body of work exploring the most cost-effective ways to intervene in childhood obesity.