Cholesterol levels have improved among children and teens in the United States over the past two decades, despite rising obesity rates during the same period, the CDC says.

Researchers analyzed data on more than 16,000 children and teens enrolled in a national health survey for the study, which appears in the Aug. 8 issue of the Journal of the American Medical Association.
Total Cholesterol Down, HDL Up

Among kids and teens between the ages of 6 and 19, significant declines were identified in average total cholesterol levels, while beneficial increases were seen in high-density lipoprotein (HDL), or good cholesterol.

The study did not explore the reasons for the improvement, but researchers say two positive trends may have played a role.

"We know that factors that contribute to blood cholesterol in children include diet, physical activity, consumption of saturated fats, and exposure to secondhand smoke," says Brian K. Kit, MD, of the CDC's National Center for Health Statistics.

He tells WebMD that the emphasis on replacing trans fats and other saturated fats with healthier fats in commercially available foods, as well as public health initiatives to reduce secondhand smoke exposure, may have contributed to the decline.
Rise in Obesity Cause for Concern

Pediatric cardiologist Sarah de Ferranti, MD, of Harvard Medical School and Boston Children's Hospital, says while there is reason for optimism in the new findings, the rise in childhood obesity during the same period remains a major cause for concern.

According to the CDC, the obesity rate among children and teens in the U.S. has tripled since 1980.

"There is certainly a concern that the obesity epidemic will overwhelm any benefits we might see from this positive trend," she tells WebMD. "As overweight kids become overweight adults, this is certain to have a negative impact on heart disease and diabetes."

American Heart Association president Donna Arnett, MD, echoes the sentiment. She is a professor and chair of epidemiology at the University of Alabama at Birmingham.

"There is reason for optimism in the finding that cholesterol levels seem to be on the decline in our youth, despite the unfavorable trend in obesity," she says. "Looking to the future, we need to do all that we can to see if this trend continues."
More Study Needed, Expert Says

The CDC researchers assessed cholesterol and blood fat levels during three time periods among kids and teens between the ages of 6 and 19.

Between the time of the first survey, conducted between 1988 and 1994, and the third, conducted between 2007 and 2010, the prevalence of youths with elevated total cholesterol levels declined from around 11% to 8%. The prevalence of teens with elevated blood fats and LDL (bad cholesterol) also decreased.

De Ferranti says future research should focus on identifying the cause or causes for the decline to guide health policymakers in the future.

"These studies could help us understand which types of interventions have the biggest impact," she says.