CANBERRA -- A visiting U.S. obesity expert, Kelly Brownell, on Tuesday called on Australia to make a start on taxing high-sugar soft drinks.

As director of U.S. Yale University's Rudd Center for Food Policy and Obesity, Professor Brownell is in Canberra of Australia to attend the 46th Australian Psychological Society Annual Conference.

He said soft drinks were a good place to start in the taxing of high-sugar foods because they were the single greatest source of added sugar in the average person's diet, had absolutely no nutritional value, were marketed aggressively and were linked with the risk for obesity and diabetes.

While obesity has overtaken smoking as the leading cause of premature death and illness in Australia, he said the government should tax soft drinks in the same way it taxes cigarettes, because research showed that taxes had been the strongest influence on falling rates of consumption.

"We have seen how effective tobacco taxes have been in reducing rates of smoking, so there is no reason to believe such taxes wouldn't be as effective in reducing the consumption of high sugar and fat foods," Brownell, who was named by Time magazine as one of the 100 most influential people in the world, told the conference in Canberra on Tuesday. "A soft-drink tax is a good place to start. "

Earlier this week, Denmark became the first country to impose a tax on food containing saturated fats, and Brownell said he completely supports Denmark's policy and that governments should act courageously to do whatever is effective in encouraging better eating habits.

According to the Organisation for Economic Co-operation and Development report, Australia is ranked as one of the fattest nations in the developed world. The prevalence of obesity in Australia has more than doubled in the past 20 years, with more than 17 million Australians are overweight or obese.