Teenage girls who are obese do not perform as well academically as their normal-weight peers, a new study has found.

UK researchers set out to investigate the link between obesity and academic attainment during the teenage years. They looked at the academic records and weight status of almost 6,000 young people aged between 11 and 16.

Almost three in four of the young people were a healthy weight, but 13% were overweight and 15% were obese.

The study found that girls who were obese at the age of 11 had achieved less academically at the ages of 11, 13 and 16, compared to their normal-weight peers.

While the average grade achieved in maths, English and science was a C, among the obese girls, this fell to a D.

However, the link between academic attainment and obesity among boys was unclear.

"Further work is needed to understand why obesity is negatively related to academic attainment, but it is clear that teenagers, parents, and policymakers in education and public health should be aware of the lifelong educational and economic impact of obesity," commented the study's principal investigator, Prof John Reilly, of the University of Strathclyde.

The study took into account factors that may have influenced the findings, such as IQ, mental health and socioeconomic status, however the results remained the same.

"There is a clear pattern which shows that girls who are in the obese range are performing more poorly than their counterparts in the healthy weight range throughout their teenage years." the researchers said.

Details of these findings are published in the International Journal of Obesity.