THURSDAY, Aug. 5 (HealthDay News) -- In a sign that diabetes may strike at the brain early in life, a small study found that obese children with type 2 diabetes suffer from thinking difficulties that do not appear in non-diabetic overweight kids.

The preliminary study doesn't definitively prove that diabetes is responsible for the differences between the children, and it's not clear if the diabetic kids suffer much from having more limited cognitive powers.

Still, the findings suggest that in diabetics, "very early on, we can already see potential brain damage developing. We have to look at the disease in a much more comprehensive way than just affecting eyes, kidneys, toes and feet," said study co-author Dr. Antonio Convit, a professor of psychiatry at New York University Langone Medical Center.

According to Convit, type 2 diabetes -- which is often caused by excess weight -- now makes up about 40 percent of cases of diabetes in children.

In the past, kids were much more likely to have type 1 diabetes, also known as juvenile diabetes. But the rise in obesity among kids has greatly boosted the number of type 2 diabetes cases.

In adults, some diabetics show signs that their abilities to learn and remember things are more limited than in other people, Convit said. But it's hard to know whether that's a result of diabetes or of heart disease that causes "plumbing problems" -- or clogged blood vessels -- in the brain, he said.

To better understand how diabetes affects the brain early in life, Convit and his colleagues tested the cognitive skills of 18 obese teenagers with type 2 diabetes and 18 teens who were also obese but not diabetic.

The researchers found that the obese diabetic teens scored more poorly than the others on tests of attention, memory and planning, Convit said. They also scored lower on IQ tests.

While the differences were statistically significant, the study doesn't combine the findings into one number, Convit said. So it's impossible to know exactly how much lower the diabetic kids scored percentage-wise.

It's possible, he said, that diabetes affects the way that vessels bring blood to the brain.

The good news is that it appears these effects fade once type 2 diabetes disappears, he said, suggesting how important it is to help obese kids lose weight.

But trouble looms for those who remain overweight. "As the rate of obesity continues to raise in children, this will be first generation who are likely to have a much diminished lifestyle and diminished quality of life because of these issues that are ultimately fixable," he said.

Roger A. Dixon, a professor of psychology who studies diabetes at the University of Alberta in Canada, stressed that the findings are preliminary.

But he added that "it's also a very promising direction of research" that can help researchers understand if there's a connection between the effects of diabetes on the brains of older adults and the effects on children and younger adults.

The study appears online in the journal Diabetologia.

More information

Learn about recipes for kids with diabetes from kidshealth.org.