Initial results from their research were presented Oct. 14 at the annual meeting of the North American Association for the Study of Obesity. The USC researchers are studying patterns of metabolic change among Hispanic children and teens.

"Obesity is now a critical, common nutritional problem in children," study presenter Michael I. Goran, professor of preventive medicine and physiology and biophysics, says in a prepared statement.

"It disproportionately affects minority groups and is the major contributor to the recent emergence of type 2 diabetes among children. We need to do something now to understand and prevent these chronic diseases," Goran says.

He and his colleagues found nine of every 10 overweight Hispanic children had at least one risk factor for cardiovascular disease and type 2 diabetes. This appears to be due to low sensitivity to insulin.

About 28 percent of overweight Hispanic children with a family history of type 2 diabetes already have pre-diabetes elevated blood sugar levels linked to beta cells that have started failing. Beta cells are cells in the pancreas that create insulin.

"We knew this was a high-risk population, but the extent of these risk factors and the magnitude of the health problem was bigger than we expected. These overweight children are effectively 'walking time-bombs,' and the metabolic basis of these risk factors must be targeted in interventions," Goran says.

It's estimated that nearly a third of Hispanic and black American children are overweight. Many are being diagnosed with type 2 diabetes -- once exclusively an adult disease -- during puberty.