The performance of a student in the classroom may be affected by how much fast food one eats. A recent study published in the journal Clinical Pediatrics found that fifth-graders who ate fast food had weaker abilities in the subject areas of math, science and reading by the time they reached the eighth grade.

According to Ohio State University and University of Texas researchers, students who ate the most fast food had test scores that were about 20 percent lower than those who didn't eat any fast food at all. They believe that the correlation is not a mere coincidence, and the data says so too.

"These results provide initial evidence that fast-food consumption is associated with deleterious academic outcomes among children," lead author of the study, Kelly Purtell says.

The study included nearly 11,740 students from the Early Childhood Longitudinal Study-Kindergarten Cohort, who were tested  in reading/literacy, mathematics and science in both the fifth and eighth grades, to establish a clear change within the students' performance levels inside of the classroom.

More than two-thirds of the students tested said they had eaten in a fast-food restaurant in the previous week. Twenty-nine per cent of the children did not have any fast food during the week before they completed the questionnaire. Though only a marginal number of the students had ever had fast-food as part of their diet.

Researchers found that children who ate fast food four to six times per week showed less impressive performance in the three areas, compared to children who did not eat any fast food the week before the survey. The researchers found that eighth-graders who ate fast food daily were behind those who ate no fast food by four points in reading. And they were behind by three points in math and four points in science too.

Children who ate fast food just one to three times a week had lower academic growth compared to non-eaters in only one subject, which is math.

"There's a lot of evidence that fast-food consumption is linked to childhood obesity, but the problems don't end there," Purtell says, "Relying too much on fast food could hurt how well children do in the classroom."

"We're not saying that parents should never feed their children fast food, but these results suggest fast-food consumption should be limited as much as possible."

According to the report, the results may have been caused by lower levels of nutrients in fast foods, especially iron, and the high levels of fats and sugar in fast food. The report also said that the link between fast-food eating and academic performance remained intact even when such variables as physical activity, television watching and socioeconomic status were included as covariants.