Ask a pediatrician and she'll say obesity in adolescent girls is a problem because it can tax the heart, lead to diabetes and strain the joints.

Ask a teenage girl and she'll say it's depressing and isolating and it makes it hard to find clothes to fit.

But ask Prof. John Reilly, professor at the University of Strathclyde in England, and he'll have a different answer: Teen girls who are obese are apt to suffer academically.

Prof. Reilly and his team assessed data from nearly 6,000 children. Four hundred sixty-six were obese females. The girls who were obese at age 11 performed worse academically at ages 11, 13 and 16 compared with those of a healthy weight.

Even factoring in differences in socio-economic status, mental health, IQ and age of onset of the menstrual cycle, the finding held up. Obese teenage girls underperform.

At this point, scientists don't know why the correlation exists. But the fact that it does is yet one more reason to fight obesity, particularly in children.

And that should be of much interest in the United States where between 16 and 33 percent of children and adolescents are obese.

Fighting obesity has proven a daunting task for individuals. Perhaps chewing on this new research will provide some incentive.