"In China in 1989 there were no overweight people," he told the Herald yesterday, before addressing 900 economists on the Gold Coast. "Now, about 25 per cent are overweight or obese." Similar patterns were appearing in most of Asia, most of urban Africa and the Middle East. "In the developing world it has clearly been a phenomenon of the last 15 years."

Professor Popkin told the International Association of Agricultural Economists that China's changing diet was following "a classic Westernisation pattern". In the past 20 years consumption of cereals had "decreased considerably", while energy obtained by eating fat had more than doubled. China's lifestyle had become more sedentary, with 14 per cent of homes acquiring a motor vehicle between 1989 and 1997, and 97 per cent now having television. "In one study we showed the odds of being obese were 80 per cent higher for men and women in households which owned a motorised vehicle."

While obesity was afflicting both developed and developing countries, there were key differences. Professor Popkin blamed an explosion in the consumption of high-calorie, sweetened beverages - "soft drinks and fruit drinks" - for much of the obesity in the United States and Australia in the past two decades. "When you consume them you do not reduce your intake of food."

But he said China's epidemic was powered by a spectacular growth in the consumption of animal foods. "Beef, pork in particular, and poultry - they have tripled in the last 12 years." Meat production had been matched by the rising use of cheap vegetable oils. Another problem was the arrival of Western-style food advertising. Professor Popkin advocated taxation, pricing and tough advertising controls, not education, as the weapons to fight global obesity.

"Telling people to eat better and be more active won't work - education can't do it," he said, adding that the example for success had been set by the battle against smoking. "We cut smoking [by] two-thirds by taxing cigarettes and increasing the price. With a calorie tax, say five cents for every added gram of sugar, you would cut consumption [of sweetened drinks] in half."