And a new time-bomb is ticking.
Obesity Australia, the nation's leading research body in the field, says that in the decade to 1995 overweight and obesity rates in children doubled to 21 per cent, and by 2012 had climbed to 26 per cent.
Within a decade one-third will be overweight and will remain fat into adulthood.
Monash University says that on the basis of present trends the life expectancy of Australian children will be shorter than earlier generations because of obesity.
Obesity Australia warns Australia can no longer wait to tackle what it describes as an epidemic.
In a major new report, Obesity: a national epidemic and its impact on Australia, it says that in 2008 the annual financial cost was estimated at A$8.3 billion ($8.9 billion).
With other accumulated costs the total bill soared to an estimated A$58.2 billion.
The report says obesity is a cause of associated disorders including Type 2 diabetes, cardiovascular disease and some cancers. It is also associated with osteoarthritis, sleep apnoea and reproductive difficulties.
It says the "epidemic" is driven by the interplay between genetics and the environment.
About 90 per cent of the population is genetically predisposed to becoming overweight and obese which, coupled with fast and "energy-dense" food and sedentary lifestyles, is pushing up obesity rates.
Obesity Australia says it is time for the condition to be treated as a disease in its own right.
"Recognition of obesity as a disease is essential to reducing the stigma around obesity, and also key to increasing community engagement in practices and policies that reduce obesity rates," the report says.
"If obesity rates continue to grow in Australia at current rates over the next decades, it is conceivable that the health and economic cost due to obesity will also grow to overwhelming proportions."
Australia's federal and state governments have declared obesity as one of nine national health priority areas and have launched a number of programmes. But Obesity Australia wants a nationwide prevention plan focused on education of both adults and children, and direct support for treatment including weight loss programmes, pharmaceutical interventions and more publicly funded bariatric surgery.
90% of Australians have a fat gene predisposing them to weight gain
63% Of adults are overweight
28% Of adults are obese
70% Of adults are expected to be overweight by 2025
A$58.2b Annual cost of obesity.
source: Obesity Australia