There's more evidence that being overweight is bad for kids with a new study finding that obese children are more than twice as likely as normal-weight children to have diabetes.

Researchers at the University of Michigan Health System in Ann Arbor also estimated that 229,000 American children have diabetes, and that a third of those diabetic children are obese. This combination of obesity and diabetes may soon strain the nation's health-care system, the researchers added.

"Among school-aged children, obese children have a greater than twofold chance of having diabetes, compared with children of normal weight," study author Dr. Joyce Lee, of the division of pediatric endocrinology and the Child Health Evaluation Unit, said in a prepared statement.

"The large number of children with diabetes in the U.S., and the potential for increasing numbers of children developing diabetes with the obesity epidemic, has serious implications for how these children will receive appropriate health care now and as they grow into adulthood," Lee said.

For their study, Lee and her colleagues analyzed 2003-2004 data from the National Survey of Children's Health. The data used for this study did not distinguish between type 1 and type 2 diabetes.

Type 1 disease is an inherited form, where the pancreas cannot produce sufficient insulin. Type 2 diabetes -- where the body gradually builds resistance to insulin -- is much more common and is usually linked to being overweight.

Diabetes rates were higher among older children, and the disease was more common among non-Hispanic white children than non-Hispanic black children or Hispanic children, the study found.

The findings appear in the February issue of Diabetes Care.

"These data create cause for concern, especially with a nationwide shortage of specialists who care for children with diabetes," Lee said. "From a clinical, public health and health resources perspective, we need to address childhood obesity head-on to help reduce the future burden of diabetes in the U.S."