Diabetes and prediabetes have more than doubled among teenagers in the United States, an alarming trend that has health experts urging parents to pay more attention to their adolescents’ eating and exercise habits.

Among adolescents ages 12-19, 23 percent now have diabetes or prediabetes, up 9 percent from a decade ago, according to a recent study published in the journal Pediatrics.

People with prediabetes have blood glucose levels that are higher than normal, but not yet high enough to be diagnosed as diabetes. They could go on to develop diabetes or they could prevent it by lowering blood glucose levels with healthier diet and more physical activity.

In the study, researchers at the national Centers for Disease Control and Prevention (CDC) looked at risk factors for heart disease and stroke in adolescents, examining data on more than 3,300 adolescents participating in a national survey from 1999 to 2008. Along with the increase in diabetes, they found that:

• 61 percent of obese teens in the survey had one risk factor for cardiovascular disease – such as high LDL cholesterol, high blood pressure, physical inactivity or diabetes – in addition to being significantly overweight.

• 49 percent of overweight teens had one additional cardiovascular risk factor.

• 37 percent of normal-weight teens had at least one cardiovascular risk factor.

The study has caught the attention of health providers researching obesity’s dangerous effects. “I think this is an eye opener,” Steven Mittelman, M.D., of the Children’s Hospital Los Angeles Center for Endocrinology, Diabetes & Metabolism, says of the study. “Parents really need to think about what their kids are eating and what their activity level is. Parents have to step up and help prevent these devastating diseases that last a lifetime.”

Here are his suggestions for parents:

• Pay attention during checkups. Doctors should be checking children’s height, weight and blood pressure at every visit, and taking the time to calculate Body Mass Index (BMI, a measure of height related to weight) for patients. Under some circumstances, they should also test kids’ cholesterol levels and test for diabetes.

• Know your family history. Let your pediatrician know if your child’s parents or grandparents have high cholesterol, diabetes or heart disease. Find out what medications your child’s grandparents take, and share that information as well. “That helps us know what might run in the family,” Mittelman says.

• Check out resources that get kids moving. Mittelman recommends the CDC childhood obesity page (cdc.gov/obesity/childhood), Michelle Obama’s Let’s Move! campaign (LetsMove.gov) and your local YMCA (YMCA.org) as great places to start.

“I often send my parents who say they have a tough time getting their kids to exercise [to the YMCA],” he says. “They really are focused on healthy weight.”

Christina Elston is a senior editor and health writer for Dominion Parenting Media. Read Health-e, her family health blog, at www.parenthood.com/healthe.php.