Although previous research has concentrated on snacking, the researchers chose to look at the nutritional quality of the food rather than when it was eaten.

The lower overall nutritional quality of diets, increased average caloric intake and decreased levels of physical activity have all been posited as significant influences.

We need crops that offer better nutritional quality, can withstand drought, use fertiliser more efficiently and resist diseases and pests.

This has coincided with a fall in the nutritional quality of foods purchased, with moves away from fresh fruit and vegetables and towards processed foods.

There's no escaping the fact that better food - measured by taste or nutritional quality - costs more because it has been grown or raised less intensively and with more care.