Within a decade, Australia's obesity epidemic is expected to impact 35 percent of the population from today's base of 28 percent.
The dramatic prediction, published in the International Journal of Obesity, is that severe obesity will also increase and women will fare worse than men.
The study was a collaboration between the University of Sydney, the Charles Perkins Centre and the George Institute for Global Health based on modelling of Australia's current levels of obesity.
Lead researcher Alison Hayes said Australia's current rate of obesity among children was part of the reason why the rate among adults was expected to increase.
An increase in childhood obesity means Australians are starting out adulthood with a higher BMI and higher levels of obesity than ever before.Alison Hayes
"Contrary to popular belief, it's not in middle age that people suddenly pile on the pounds," Hayes said.
"In fact, at a population level, young people gain more weight each year than older people. But for most of us weight gain tends to be cumulative and so we're more likely to move into an overweight or obese category later in life.
"An increase in childhood obesity means Australians are starting out adulthood with a higher BMI and higher levels of obesity than ever before.
"For example, in 1995 around one in 10 young adults were obese, but in 2014 it was closer to one in five. We're also living longer, and most sectors of the population gain weight throughout their life."
Hayes said the study should be a wake-up call to all Australians to look at ways of reducing obesity in today's children, lest these predictions came true.
"We know an increase in obesity and severe obesity will result in higher rates of chronic disease such as type 2 diabetes, cardiovascular disease and cancer, with an increased strain on the health system and healthcare costs," Hayes said.
"Any reduction in the incidence of obesity going forward will have beneficial impacts on population health and the healthcare costs, but the model can help establish where our efforts should be prioritised."