问答题 Americans are used to being warned for their self-destructive fondness for cheese-flavored snacks(有乳酪味道的快餐). But citizens of developing countries are also unable to escape the danger of the First World's fat-rich diet and couch potato ways. At last week's 8th International Congress on Obesity(肥胖), held in Paris, researchers warned that the planet's expanding waistlines threaten "to become the curse of the next millennium(千年)".
"We used to consider obesity a problem of industrialized, rich countries," says Arnaud, a member of the meeting's lead committee. "But now it has become a world disease."
Researchers blame the trend -- and the attendant rise in the incidence of heart disease and diabetes(糖尿病) -- on the Third World's increasing wealth, reduced physical activity, and more calorie-laden diets. As a result, the World Health Organization has estimated that 300 million people will be obese by 2025, an increase of 50 million from today. In Mauritius, for example, WHO estimates that 32 percent of the population will be obese by 2025, compared with 7 percent in 1987. Last year, WHO said that obesity's fatal impact could rival smoking.
There was much hopeful discussion about new drugs such as leptin, a hormone that has proved effective for severe weight problems. But leptin should be a last resort, says Basdevant: "First of all, we have to consider prevention." If America is any indication, however, educating the world about the danger of Big Macs and cable TV will be difficult: despite heightened awareness of the need for proper diet and exercise, the number of obese Americans is expected to double over the next three decades.

1.What are Americans warned for?