Flying in the face of conventional thought, overweight children have fewer cavities and healthier teeth compared to other kids, a new study finds.

Scientists are clueless as to why.

Researchers at the Eastman Dental Center, part of the University of Rochester Medical Center, analyzed data on nearly 18,000 children who participated in two separate National Health and Nutrition Examination Surveys.

Children ages 6-18 who were considered overweight or at risk for becoming overweight showed a decreased risk of tooth decay compared to their normal-weight peers.

"We expected to find more oral disease in overweight children of all ages, given the similar causal factors that are generally associated with obesity and [tooth decay]," said Dr. Dorota Kopycka-Kedzierawski, the lead author of a paper published in this month’s issue of Community Dentistry & Oral Epidemiology.

"Our findings raise more questions than answers," Kopycka-Kedzierawski said. "For example, are overweight children eating foods higher in fat rather than cavity-causing sugars? Are their diets similar to normal weight peers but [perhaps they] lead more sedentary lifestyles? Research to analyze both diet and lifestyle is needed to better understand the results."