A small animal study suggests that food intake in satiated rats is triggered by an optimal fat to carbohydrate ratio, which may be the key determinant of the rewarding properties and palatability of the snack food making it highly appetizing.

Researchers conducted behaviour preference tests and gave 18 rats access to standard rat feed and test foods of various content of fats and carbohydrates. They also performed magnetic resonance imaging (MRI) measurements to investigate modulation of whole brain activity induced in the rats during the tests.

They found that the foods with a composition most closely resembled that of potato chips were most appetizing to the rats, and these foods influenced brain activity patterns in regions associated with reward and addiction.

Previous studies in which rats were fed potato chips have shown that foods that are high in calories, fats or carbohydrates seem to modulate activity in the brain reward system, and can drive increased feeding triggering excessive food intake beyond normal satiety. It was thought that energy content may be the key behaviorial determinant.

However, researchers of this study suggest that it is the ratio of fat to carbohydrate, not the absolute energy content, that seems to make the foods highly appetizing...at least to the rats.