Few children in the study had actual diabetes, but the level of risk factors was "very high," said study co-author Dr. Francine Kaufman of Children's Hospital Los Angeles.

The study included a large number of Hispanic and Native American children -- ethnic groups that have a particularly high rate of type 2 diabetes -- and these students had the highest fasting blood sugar levels.

Dr. Kaufman stated that, “The findings add to evidence that excess pounds and inactivity are putting more and more U.S. children, particularly minorities, at risk of diabetes.

"This really screams for us to do comprehensive prevention," she said.

That can include healthier foods and a return to physical activity at school, according to Kaufman, as well as efforts in the community -- like creating safe places for children to get some exercise -- and at home.