The more overweight children and teens are, the more numerous and severe their headaches, according to a U.S. study.

But losing weight eases the frequency and severity of the headaches, the researchers said.

The study, conducted at seven pediatric headache centers, found that 34.1 percent of patients were either overweight (17.5 percent) or at risk of becoming overweight. That's similar to rates of overweight in the general child/teen population.

The researchers analyzed data collected on 913 patients at the start of the study, and again at three and six months, and found evidence of a link between weight and headaches.

"Among children who are overweight at their initial headache center visit, a change in their body mass index (BMI) was associated with a change in the frequency of their headaches over time," study lead author Dr. Andrew Hershey, director of the Headache Center at Cincinnati Children's Hospital Medical Center, said in a hospital news release.

"While we can't claim a causal link between obesity and headache, the association suggests some physiological or environmental processes that are common to both conditions," he said.

The findings, published online in the journal Headache, have important implications for clinical practice, according to Hershey.

"Physicians should actively consider a child's weight in the context of treatments for headaches," he said. "They should routinely assess weight and BMI and be prepared to offer weight control information at the initial treatment visit."