China is super-sizing its children as fast as its economy, prompting fears of an American-style obesity crisis here.

New figures from the Health Ministry show that urban Chinese boys age 6 are 2.5 inches taller and 6.6 pounds heavier on average than Chinese city boys 30 years ago.

China "has entered the era of obesity," says Ji Chengye, a leading child-health researcher. "The speed of growth is shocking."

A generation of economic expansion has produced higher living standards and allowed Chinese families to put more food on the table; once-scarce meat, dairy products and vegetables now are widely available. Growing prosperity also has led to more sedentary lifestyles: less physical labor, fewer trips on foot and by bicycle, more travel by car, more Internet usage.

The average 6-year-old in Beijing or Shanghai weighs nearly 47 pounds and is 3 feet, 10.5 inches tall, ministry figures show. The average American of the same age weighs just over 50 pounds and also is 3 feet 10.5 inches tall, according to data from the U.S. Centers for Disease Control and Prevention.

Only 45 years ago, China was still in the grip of a massive famine. Disastrous government policies under Mao Zedong led to the starvation deaths of 30 million people. Malnutrition has been stamped out in cities, but UNICEF says it remains a problem among millions of rural poor, especially in western China.

Most of the growth spurt among Chinese children has taken place over the past decade. "The speed of the increase greatly exceeds the growth trends found in Western developed countries," said Yang Qing, director of the Health Ministry department that oversees child health issues.

Today, 8% of 10- to 12-year-olds in China's cities are considered obese and an additional 15% are overweight, according to Education Ministry data. The closest comparison, in a 2006 report by the U.S. Department of Health and Human Services, found that 18.8% of Americans between the ages of 6 and 11 are overweight. There was no separate breakout for obesity among American children.

Bigger children are a source of pride and proof of prosperity for many Chinese. "The old saying, 'A fat child is a healthy child,' is still too prevalent," Ji says.

The government is fighting juvenile flab, in part, by building more playgrounds and requiring students to exercise or play sports for an hour a day at school.

Chen Chunming, a nutritional expert at the Chinese Center for Disease Control and Prevention, warned parents, "Don't take children to eat fast food like McDonald's and KFC." McDonald's and KFC have hundreds of outlets in China, as do other American fast-food companies.

McDonald's wants to promote "balanced, active lifestyles" and has sent corporate icon Ronald McDonald to schools throughout China to "get kids up and active," said Gary Rosen, chief marketing officer for McDonald's China.

Last week at a McDonald's in Beijing, salesman Liu Guojian beamed while his daughter Xinyi, 7, ate a hamburger.

"Our daughter will definitely be taller than us. She has eaten better than my wife and I," Liu said. "When I grew up, in winter all we had to eat was cabbage."