Obesity not only affects a child's overall health, but also their grades, Georgian researchers say.

Girls, who are obese during their adolescent years, are more likely to fare poorly in academics throughout their teens, according to a University of Strathclyde, Dundee, Georgia study.

For the study, the researchers examined data from almost 6000 children from the Avon Longitudinal Study of Parents and Children (ALSPAC). They compared their body mass index from ages 11 to 16 with their performance in national tests during those years. Among the study group, 71.4 percent were healthy weight (1935 male, 2325 female), 13.3 percent overweight (372 male, 420 female) and 15.3 percent obese (448 male, 466 female).

The experts found that obese girls had poor academic performance at 11, 13 and 16 years when compared to their normal and healthy counterparts. For example, obese girls scored a D in core subjects of English, Maths and Science instead of a C, which was the average 'poor' grade among the students.

The researchers also considered factors such as socio-economic deprivation, mental health, IQ and menstruation cycles in the study, but found that they failed to change the relationship between obesity and academic achievement.

The researchers however could not establish a link between obesity and academic accomplishment in boys.

 "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," John Reilly, Professor of Physical Activity and Public Health Science and the Principal Investigator of the study, said in a statement.

The finding is published in the International Journal of Obesity.

Reilly said that although the study focused on British teens, the findings are also applicable to teens in the United States. Obese children between the ages 12 and 19 accounted for 5 percent of the obese in 1980, but the figure grew to nearly 21 percent by 2012.

"The similarities between the environment, the culture, [and] school systems between the U.S. and the U.K. are more similar than may be obvious," Reilly said, npr reports.

Echoing similar sentiments, David Katz, the director of Yale University's Prevention Research Center, who wasn't involved in the study, said that there is nothing about this [study] that is specific to the U.K.