The rapidly increasing number of overweight Australians has seen the country overtake Canada in the obesity rankings, with 28.3 percent of adults tipping the scales.
Australia is behind the United States, Mexico and New Zealand in the OECD's annual ‘Health at a Glance’ report.
Despite this, Australia ranks 18th when it comes to children being overweight, below the OECD average.
The OECD shows a negligible gender gap for obesity in Australia, while women in countries like Mexico, Chile, South Africa and Turkey are much more likely to be overweight.
Australia is number one for fruit and vegetable consumption, while Finland, which has substantially fewer obese people, is at the bottom of the rankings.
Australia also has one of the lowest rates of smoking, with only 15 percent of people having a cigarette daily.
Life expectancy at birth in Australia is 82 years old, the seventh best in the OECD and two years higher than average.