The contents of a lunch box can say a lot about a child's future.

High-fat, high-calorie diets can set the stage for diabetes, heart disease and depression from an early age.

Obesity can even reduce a child's cognitive performance, researchers at the University of Bristol found.

According to a study by the Robert Koch Institute (RKI) from 2018, every seventh child in Germany is overweight or even obese.

In theory, there is general agreement that school canteens in particular offer an enormous opportunity to take countermeasures.

But how do you do it?

Scientists at the Max Planck Institute for Research on Collective Goods in Bonn have tested a new concept so that children can also recognize for themselves which foods are healthy.

Her approach: award school grades for the snack during the break.

The experiment worked in twelve Spanish elementary schools: It showed that the children in the third and fourth grades adjusted their eating behavior positively if they knew which meal would bring a good grade.

If their parents were also informed about these grades, this proved to be a clear intensifier of the effect in the experiment.

"We wanted to start the competition for good grades"

For the experiment, the researchers set up baskets with different foods for three weeks and labeled them with Spanish notes.

The basket with chocolate rolls and orange juice received a zero (insufficient), while the basket with banana, ham sandwich and water received a grade of ten (very good).

“We wanted to keep it as simple as possible.

According to the current state of knowledge, school grades do not leave as much room for interpretation as, for example, food traffic lights," explains behavioral economist and study author Matthias Sutter.

282 primary school children were assigned to four groups: In a control group, the children were allowed to choose four foods from the baskets without being influenced.

Children in the second group had previously heard a lecture by a nutritionist.

Children in the third group were confronted with the grades.

"We wanted to start the competition for good grades because children compare themselves," says Sutter.

Group dynamics spur the children on, so the assumption.

Since children also often want to impress their parents with good grades, the researchers added a fourth group: In the so-called "parents treatment", the parents of the nine to ten-year-olds were told weekly which snack - converted into an average grade - their child wanted had decided.

Parents should have a say in school lunches

The result: 74 percent of the children whose parents were informed chose healthy foods.

With an average grade of 7.9, the children from the parent group were ahead.

The worst performers were those children who received no intervention at all: Only 36 percent chose healthy snacks.

The other two groups were in between – the proportion of healthy meals here was less than half.

Four months later, the behavior of the students was essentially unchanged.

Around 70 percent of the children from the parents' group still chose healthy food.