It had been thought animals were attracted purely by chips’ high calorie and fat content, but when tested against high-fat pellets, scans showed chips affected the addiction parts of the rodents’ brains.

The rats were far more keen on the chips, despite the fat and carbs mixture containing the same number of calories.

Tobias Hoch, of Germany’s University of Erlangen-Nuremberg, said, “There must be something that makes them desirable.

"Recreational over-eating may occur in almost everyone at some time in life. "

His team now plans to find these triggers to help create anti-obesity drugs.

The scientific name for not being able to put down a packet of chips or biscuits is "hedonic hyperphagia."