A quarter of Australian children aged between five and 17 are either overweight or obese, figures published on Thursday indicated.
The data from the Australian Bureau of Statistics (ABS) also showed that the nation's kids spend an average of two hours a day in front of the television or computer.
The ABS said the increase in obesity was most marked in boys, with the rate doubling from five to 10 percent between 1995 and 2007-2008.
The number of overweight but not obese children remained steady at about 17 percent.
"Overweight and obesity, in both children and adults, is a major health concern," the ABS said.
"The rates were much higher for adults, with 61 percent of Australian adults overweight or obese in 2007/08."
Australian children were spending on average two hours per day playing video games or watching television, the maximum recommended under national guidelines, the bureau said.
"Around 45 percent of children who watched television, videos or DVDs, and 10 percent of children who played electronic or computer games, did so for 20 hours or more over the two-week (survey) period," it said.
Of the children surveyed, 97 percent had watched television, videos or DVDs in the previous fortnight, and 64 percent had played electronic or computer games, the ABS said.
An estimated 37 percent of children aged five to 14 did not partake in any form of sport, even backyard games, it added.
"Obesity not only has significant health and social impacts, but also considerable economic impacts," the ABS warned.
"In 2008, the total annual cost of obesity for both children and adults in Australia, including health system costs, productivity and carers' costs, was estimated to be around 58 billion dollars (50.7 billion US)."