Telling a child why a healthy food is good for them may backfire and lead to them eating less of it, a new study suggests.

"We predicted that when food is presented to children as making them strong or as a tool to achieve a goal such as learning how to read or count, they would conclude the food is not as tasty and therefore consume less of it," researchers from Chicago in the US said.

They decided to test this theory out. They carried out five studies on children aged between three and five. In all five studies, the children were read a story book with pictures about a little girl who consumed either carrots or crackers.

Depending on the study, some of the children were told about the benefits of the snacks, such as they made the girl strong, while some children did not hear about the benefits.

Each child was then given an opportunity to consume the snack that had been mentioned in the story and the amount they ate was measured.

The study found that the children consumed larger amounts of the snack if they were not given any healthy messages about it.

"Parents and caregivers who are struggling to get children to eat healthier may be better off simply serving the food without saying anything about it," the researchers concluded.

Details of these findings are published in the Journal of Consumer Research.