Fast food is already blamed for all sorts of health problems, from obesity to bad skin, and now a new study has found that it could actually slow down the brain.

According to research, children who eat the most fast food are found to have poorer scores in tests for maths, science and reading.

One theory suggested by researchers is that a lack of iron – which is associated with fast food – leads to a slowing in development of certain processes in the brain.

New research has found children who eat the most fast food are found to have lower scores in tests

Another idea is that diets high in fat and added sugar have a negative impact on the learning process.

Dr Kelly Purtell who led the study at Ohio State University, said: ‘Research has been focused on how children’s food consumption contributes to the child obesity epidemic.

One theory suggested by researchers is that a lack of iron, which is associated with fast food, leads to a slowing in development of processes in the brain

‘Our findings provide evidence that eating fast food is linked to another problem: poorer academic outcomes.’

The research used data from a national representative sample of 8,500 schoolchildren from the USA, whose fast food consumption was measured at the age of ten.

This was then compared against academic test results three years later, after taking into account more than two dozen other relevant factors.

Children were asked how many times they had eaten a meal or snack from a fast-food restaurant, including McDonald’s, Pizza Hut, Burger King, and KFC.

Fifty two per cent had eaten fast food between one and three times in the previous week and ten per cent had eaten it four to six times.

Another ten per cent had eaten it every day.

In science the daily eaters scored an average of 79 points, compared to 83 in those who never ate fast food.

Similar differences in academic achievement were observed for reading and maths.

Last year Australian researchers revealed eating fast food can have a detrimental effect on memory — in rats, at least.

Scientists at the University of New South Wales showed that rats fed a diet high in fat and sugar suffered inflammation of the hippocampus, the area of the brain associated with verbal and spatial memory.

Spatial memory helps you remember things, such as the layout of your town.