“It’s frightening how severe this metabolic disease is in children,” said Dr. David M. Nathan, an author of the study and director of the diabetes center at Massachusetts General Hospital. “It’s really got a hold on them, and it’s hard to turn around.”

Before the 1990s, this form of diabetes was hardly ever seen in children. It is still uncommon, but experts say any increase in such a serious disease is troubling. There were about 3,600 new cases a year from 2002 to 2005, the latest years for which data is available.

The research is the first large study of Type 2 diabetes in children, “because this didn’t used to exist,” said Dr. Robin Goland, a member of the research team and co-director of the Naomi Berrie Diabetes Center at Columbia University Medical Center in New York. She added, “These are people who are struggling with something that shouldn’t happen in kids who are this young.”

Why the disease is so hard to control in children and teenagers is not known...