A former Pringles employee revealed that the iconic Pringles tube has been intentionally engineered to keep us wanting more.

In a BBC two-part documentary, Irresistible: Why We Can't Stop Eating, Sensory Food Consultant Professor Barry Smith told Doctor Chris van Tulleken that the packaging was designed that way to encourage the evolutionary part of the brain responsible for foraging.

By creating tubes that are too small for our hands, it mimics the sensation of foraging.

"When I worked for Pringles, they were really worried about the competition from Doritos, and they were trying to think of ways to innovate," he said.

"One idea was let's make the tube bigger so that we can get our whole hand in there.

"And I said, 'No, no, don't do that'. People like struggling to have to get their hand in. They're like foraging bears. They're trying to extract the food.

"And that searching out something to eat, that's increasing your desire." Professor Smith also explained that eating is a "multi-sensory experience. There's the look of the food, the smell of the food, there's the feeling of the food on your fingers," he said.

"Even the sound of food matters.

"When you open a fizzy soda, you've got two noises. You've got the click and the tear. Sound engineers and manufacturers work really hard to get that sound just right and that's sonic branding."