Foods such as fruit and salad could appear more attractive to children if psychology and economics were applied to school cafeterias, according to research.

In a select set of schools, sales of salad increased by 100 per cent after the food was stored in a colourful bowl, while positioning chocolate milk behind plain milk caused sales of plain milk to rise, according to research by Cornell University, USA.

Also, creating a fast express service for students that were not buying junk food helped to increase the sales of healthy sandwiches.

Chris Wallace, food service director for the Corning, New York School District, said: "It's not nutrition until someone eats it. You need to have foods that kids will eat, or they won't eat – or they'll eat worse."

This news comes after a study by the University of Texas Health Science Center last month claimed that sugary drinks have a detrimental effect on children that attempt to maintain a healthy lifestyle.

The research suggested that water is a better substitute, as it can "replenish lost fluids".