(CNN) Nearly a quarter of young adults and a fifth of adolescents in the United States have prediabetes, according to a study published Monday in the journal JAMA Pediatrics.

Prediabetes -- a condition wherein blood sugar levels are elevated, but not high enough to warrant a diagnosis of Type 2 diabetes -- was estimated at 18% among adolescents ages 12 to 18, and 24% among young adults ages 19 to 34.

Experts say these numbers have risen over the past decade, putting young people at risk of developing Type 2 diabetes, heart disease and other conditions down the line.

"Until recently, young children and teens almost never got type 2 diabetes, which is why it used to be called adult-onset diabetes," says the US Centers for Disease Control and Prevention, where most of the new study's authors are affiliated. "Now, about one-third of American youth are overweight, a problem closely related to the increase in kids with type 2 diabetes, some as young as 10 years old."

More commonly associated with children has been Type 1 diabetes, an autoimmune condition in which the pancreas doesn't produce much, if any, insulin. In Type 2 diabetes, which develops over years and has been linked to obesity, the body becomes less responsive to insulin, which the body needs to balance glucose in the bloodstream.

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