Adolescents who eat a lot of fast food do 20% worse in standard tests of reading, math and science as compared to those who ate none, research finds.
The more frequently children ate fast food at around 10-years-old, the worse their test scores were three years later.
The study included data from 11,740 US students.
Around 10% reported eating fast food every day, while a further 10% ate fast food almost every day.
Over half of the children ate fast food 1-3 times a week.
Less than one-third never ate any fast food.
Dr Kelly Purtell, the study’s first author, said:
“There’s a lot of evidence that fast-food consumption is linked to childhood obesity, but the problems don’t end there.
Relying too much on fast food could hurt how well children do in the classroom.”
The researchers took into account all sorts of other factors in their study, such as how much TV they watched, what other foods they ate and the characteristics of their school and neighbourhood.
Dr Purtell said:
“We went as far as we could to control for and take into account all the known factors that could be involved in how well children did on these tests.”
It is not known exactly why fast food is linked to these problems.
However, it is likely due to a lack of nutrients such as iron, that help cognitive development.
High-fat, high-sugar diets are also bad for memory and learning processes.
Dr Purtell said:
“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.”
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The study was published in the journal Clinical Pediatrics (Purtell & Gershoff, 2014).