Why do snacks
taste better
when hungry?

The full narration of the video.

Same bag of chips. The first one, eaten hungry, makes you close your eyes. Halfway through, the very same chip just isn't as good. The chip didn't change: same salt, same oil. What changed is you. Scientists actually tested this.

Have a hungry person taste some sugar water and rate it: pretty nice. Then have him drink a big glass of sugar water and taste again a bit later: the score drops, and some find it sickly. The sweetness on the tongue is about the same. What changed is the score in his head.

Picture your body as a little shop with a buyer inside. How good something tastes is the price he'll pay for it. When the storeroom is empty, that is, when you're hungry, he bids high for food.

Researchers showed food photos to people who were hungry or full. When hungry, at the sight of rich, sweet food, the brain areas that handle wanting were more active. Hunger also sends out a 'feed me' signal. Give people extra of it in an experiment, and they sniff smells harder. So why are salty, crunchy, oily things the best of all?

Because the buyer's price list was written a very long time ago. Back then food was hard to find. A gram of fat gives the body nine units of energy, sugar and starch only four; and salt was rare out in the wild. So those two always got his top price.

And crunch? Crunch is like a quality check you can hear. In one experiment: turning up the sound of people's own bites made the chips seem crisper and fresher. So why does it stop tasting great halfway through? Once the storeroom has enough of that one thing, the buyer cuts its price.

Studies found that after eating one food until full, its score drops the most; foods you haven't touched drop much less. That's why, stuffed, you can still find room for dessert. Here's where the shop idea breaks down: a real shop changes prices with the market; your body's price list is stuck in the age of not enough food.

Now snacks fill every shelf, yet when you're hungry it still pays top price. So here's a small trick: don't pick snacks while you're hungry. In one experiment, people chose snacks to receive a week later: those who chose while hungry picked more junk food.

Eat a proper meal first, and chances are you'll want it a lot less. And this scoring isn't just about food: chilled to the bone in winter, a hot shower is bliss; in the peak of summer, you'd run from the same hot water. How good something feels isn't only about the thing; it's about what your body is short of right now.

Where else have you found that something feels extra good when you're short of it?