A 2005 WHO study found that just over 20% of Australian adults are obese, which is expected to rise to roughly 29% in 2010 if current trends continue. In the 2005 National Health Survey, 53.6% of Australians reported being overweight (above a 25 BMI), with 18% falling into the obese category (above a 30 BMI).n 2005, a study was conducted by the Australian Bureau of Statistics that compared the results of a 2004-05 survey with those conducted in the preceding 15 years. The results showed an increase in the number and proportion of adults who are overweight or obese.