Cholesterol levels are falling in children and teenagers across the United States and it's baffling experts.

A study of more than 16,000 children and teenagers, aged between 6 and 19 years old, from 1988 to 2010 tested for cholesterol levels.

Researchers from Centers for Disease Control and Prevention (CDC) found that between 1988 and 1994 as well as 2007 and 2010, there was a decrease in total cholesterol levels in general while there was an increase in high-density lipoprotein or good cholesterol. The prevalence of total cholesterol during these two periods of the study declined from 11 percent to 8 percent.

Having high-density cholesterol is good for health because it can absorb the low-density lipoprotien or "bad cholesterol" and take it back to liver. High levels of HDL cholesterol in the body significantly lowers the risk of heart disease and stroke.

Previous research has shown that cholesterol levels among U.S teens have remained normal despite the rise in obesity.

Researchers haven't given the reason about why cholesterol levels are declining in children.

"We haven't really made big inroads there despite all the work we have been doing. We may reap some small benefits from improved cholesterol levels, but obesity is going to continue to lead to type 2 diabetes and heart disease in and of itself," said Dr. Sarah de Ferranti, director of preventive cardiology at Children's Hospital Boston, reports Reuters Health.

According to estimates, almost 17 percent of the U.S children are obese or overweight. Experts blame unhealthy lifestyle and poor diet as causes of this obesity epidemic.

"Many unhealthy foods we consume in excessive amounts are cheaper because of government subsidies," Dr. Thomas B. Newman of the University of California, San Francisco told Reuters Health. Newman also said that changing the unhealthy lifestyle is a better way to fight obesity and cholesterol levels instead of spending billions of dollars on the proposed mandatory cholesterol check-ups for children, Reuters reports.

The present study is published in the Journal of the American Medical Association.