Doctors in central China are puzzling over a 10-month-old baby boy who weighs 20 kilos (44 lbs) -- about as much as a normal child of six years -- but is otherwise healthy, state media reported.
The infant, whose name was not given, was brought to a children's hospital in the Hunan provincial capital of Changsha earlier this month with a fever, the China News Service said.
Doctors were startled at the child's enormous size, which his parents attributed to him spending his days either breast-feeding or sleeping.
A photo posted on Hunan news website rednet.cn showed an obese child sitting in a crib and playing with a toy as he smiled happily at the camera.
The website described him as a "Michelin baby", after the familiar mascot of the Michelin tire company.
It said the child's cheeks resembled "two plump cuts of meat, like a mouth filled with two small balloons," while his arms and legs resembled "stacked hula hoops of fat".
Doctors told the China News Service they could find no medical reason for his extreme size.
But they said the child embodies the country's growing obesity problem, and warned parents to guard against excessive weight gain by their children, lest it lead to health problems.
Chinese waistlines are expanding rapidly as the nation develops, a problem blamed on richer diets and the increasingly sedentary lifestyles that come with growing affluence.
There are more than 60 million obese people in China, and another 200 million who are overweight, according to a Chinese health ministry statement last year that cited a 2004 nationwide survey.
Children are at special risk, according to previous reports that blame an education system in which students must spend long hours studying for high-stakes school exams, discouraging outdoor play.