During the study, juvenile and adult mice were fed a diet high in saturated fat, which is commonly found in fast foods, charcuterie and butter.

After just four weeks researchers observed impaired cognitive function in the younger mice.

However no such changes were seen in mature mice on the same diet.

Mice and humans are comparable since the brain’s prefrontal cortex – the area of the brain that controls learning, memory and personality – has similar functions in both mammals and does not fully develop in either until early adulthood, said researchers in a statement.

“As it matures, the prefrontal cortex is therefore vulnerable to negative environmental experiences such as stress, infections and trauma, or even – as the study suggests – a poorly balanced diet,” they said.

Damage can create cognitive deficits and personality changes, for example a person may have learning difficulties, lose their inhibitions or become aggressive, childish or compulsive.

Though the fatty diet did not affect the adult mice in the same way, this “does not rule out the possibility that a high-fat diet may also be harmful for the brains of adult mice,” said Urs Meyer, a professor at ETHZ.

Meyer pointed out that the excessively high-fat diet fed to the mice was not typical of the amount consumed by most people.

“Only very few children and adolescents consume high-fat diets so excessively,” said Meyer.