You finish a full meal and are like…

I'm never eating again.

But then, out comes a beautiful piece of cake.

And, well….

You said you were full!

Not for dessert.

Turns out, you really can make "room" for dessert.

And there's a scientific reason why.

The thing that gives you room for dessert is called "Sensory-Specific Satiety".

Satiety! It's one of those words.

That's Dr. Barbara Rolls.

She's a nutritional scientist, and she's been studying Sensory-Specific Satiety since the 80s.

It's a really important, basic, and very reproducible finding about human eating behavior.

Dr. Rolls says it's why we often misunderstand that "full" feeling.

So, to see it in action, we ran an experiment similar to ones she's done before:

We gave six people a giant plate of mac and cheese...

Wow, that is a lot of macaroni and cheese.

- ...and told them to eat until they were full.　- I'm done.

And then, for the second course, we gave them… more.

Nooo!

I'm not happy with this experiment.

- Then, on a different day, we did it all over again.　- I'm getting full.

Except this time, after they were full, we gave them ice cream.

Ice cream!

Yes.

Yeah, I'm done.

On average, after they said they were full on mac and cheese, each person could eat just one more ounce of it in their second serving.

I got a solid two bites in.

But when we gave them ice cream instead, somehow they could eat three times as much.

They made "room" for dessert.

The experiment shows that when you feel full, it's not necessarily that your stomach is physically full.

It's more about how interested you are in eating more.

Sensory-specific satiety is that change in how much you like a food, how much of a food you want to eat, as you're eating it.

And to really show that, we asked our participants to rate, on a scale of ten, their interest in mac and cheese before their first course...

Probably like a six.

Five.

I love macaroni and cheese, so... 25.

...and after.

I can't eat anymore.

Probably like a one.

Yeah, zero.

They all started pretty interested in the mac and cheese.

But after their first course, they were less interested.

Even less so after their second helping.

But we also asked them, throughout the experiment, to rate their interest in ice cream.

And even after getting full on mac and cheese, they stayed interested.

The only thing that made them lose interest in ice cream, was having ice cream.

"I've just had enough of that food, I want something else" is really what Sensory-Specific Satiety is.

And that instinct has a purpose: It's meant to keep us healthy.

So, it's a good thing; we're omnivores and we need to eat a variety.

So, it's gonna help to guarantee that you're gonna eat the variety of nutrients that you need.

It also means that there are certain situations where it makes us extra susceptible to overeating.

It can backfire, though, of course, because if we are presented with a variety of foods, it encourages us to keep eating.

Ever eat too much at a buffet or on Thanksgiving?

Yeah, me too.

That's because, when we have a lot of variety, we stay interested in eating for longer.

This change in the appeal of foods during a meal keeps us going, keeps us eating.

In another experiment, Dr. Rolls gave different four-course meals to two groups:

One where every course was the same food, and one where every course was very different.

The people with different foods ate 60% more.

Sensory-Specific Satiety is why you'll eat more french fries with condiments than without.

Why you'll eat more ice cream if you get multiple flavors than just one.

It's also why kids will eat more veggies if they can eat a variety of them together than if they only have one option.

That's interesting.

And it only took me eating a ridiculous amount of mac and cheese to learn it.