The chips and fries and cheeseburgers your teenager loves to eat doesn't just put him or her at risk for becoming overweight or obese. It may also lead to mental problems and abnormal brain function.

Several forms of cognitive functions could be adversely affected, including memory and behavioral flexibility.

High-fat diets deplete levels of an important protein called reelin that helps synapses in the brain function properly, a new study finds. Synapses allow nerve cells to pass signals to other nerve cells and make speedy mental, physical and sensory processing possible. As a result, several forms of cognitive functions could be adversely affected, including memory and behavioral flexibility.

A Key Protein Depleted by Fat

Mice that were fed high-fat diets showed cognitive defects as early as four weeks after they started eating the diet. The changes were apparent even before the mice began gaining weight and were seen only in adolescent mice, not adult mice who were fed the same diet.

“Our study highlights that the quality of the food eaten by teenagers may also be particularly important for an optimal maturation of the prefrontal cortex,” Marie Labouesse, lead author of the study, said in a statement.

High-fat diets can reduce problem solving and working memory, particularly in adolescents.

To understand the molecular mechanisms behind their observations about reelin, researchers focused on the prefrontal cortex, the part of the brain that controls planning complicated actions, decision making, social behavior and the expression of one’s personality. Past studies have suggested that high-fat diets can reduce problem solving and working memory, particularly in adolescents.

A Vulnerable, Developing Prefrontal Cortex
The prefrontal cortex of the brain does not mature until early adulthood. The immaturity of the prefrontal cortex makes this area of the brain sensitive to less-than-ideal experiences like trauma, too much stress or drug abuse.

The exact mechanism that causes reelin neurons to become depleted during the teen years is not fully understood, but this study suggests that eating excessive amounts of fatty foods could fire up harmful changes in the development of the prefrontal cortex, making it impossible to reach optimal maturity and causing teens who eat high-fat diets to develop intellectual deficits.

“Our findings that high-fat diets during adolescence disrupt functioning of the adult prefrontal cortex suggest that a careful nutritional balance during this sensitive period is pivotal for reaching the full capacity of adult prefrontal functions,” says Labouesse. “Although we still need to find out the exact mechanisms by which reelin neurons get depleted during adolescence, it looks like high-fat foods could kick-start changes in how the prefrontal cortex of younger people develops.”

Given the decline in the quality of diets over the last few decades and our growing understanding of the impact of poor diets on neurons, this study is cause for concern. And, of course, high-fat diets are not particularly good for adults, either.

Adolescence is a time of huge physical changes and increased calorie needs that stimulate big appetites. And it’s a time when teens start making their own decisions about what to eat, so you may want to share this study with the adolescents in your life. Information is one of the best ways to ensure kids make good choices.

The study is published in Molecular Psychiatry.