Nearly half of the children in North and South America will be overweight by 2010, up from about 28 percent today, according to a report published by the International Journal of Pediatric Obesity.
In the European Union, about 38 percent of all children will be overweight if present trends continue — up from about 25 percent in recent surveys, the study said.
"We have truly a global epidemic which appears to be affecting most countries in the world," said Dr. Philip James, chairman of the International Obesity Task Force and author of an editorial in the journal warning of the trend.
The percentages of overweight children also are expected to increase significantly in the Middle East and Southeast Asia. Mexico, Chile, Brazil and Egypt have rates comparable to fully industrialized nations, James said.
He estimated that, for example, one in five children in China will be overweight by 2010.
"They're being bombarded like they are in the West to eat all the wrong foods. The Western world's food industries without even realizing it have precipitated an epidemic with enormous health consequences," he said.
James said living in isolated areas was no longer a safeguard to securing quality of life or traditional eating habits.
He said children are "being exposed to the world's marketing might," arguing that governments should step in. "There needs to be a ban on all forms of marketing, not just television adverts."
Researchers analyzed a variety of published medical reports on obesity from 1980 to 2005 and World Health Organization data. They were able to track the growth rate of obesity in school-age populations in 25 countries and in preschoolers in 42 countries.
Researchers concluded that the prevalence of childhood obesity increased in almost all the countries for which data were available, a trend fueled by more sedentary lives and the increasing availability of junk food, among other factors.
The public health consequences of the trend alarm experts, said Dr. Phillip Thomas, a surgeon unconnected to the study who works extensively with obese patients in the northwest England city of Manchester.
Because obese children tend to carry the problem into adulthood, Thomas and other doctors say they will tend to be sicker as they get older, suffering from heart disease, stroke and other ailments stemming from their weight.
"This is going to be the first generation that's going to have a lower life expectancy than their parents," Thomas said. "It's like the plague is in town and no one is interested."
Another doctor who examined the journal report was Dr. Brian McCrindle, a childhood obesity expert and professor of pediatrics with a pediatric hospital in Toronto.
He warned that the looming problem must be addressed.
"The wave of heart disease and stroke could totally swamp the public health care system," he said.
He warned that lawmakers had to take a broader view of the looming problem — and consider doing things such as banning trans fats and legislating against direct advertising of junk food toward children.