You know the feeling. You finish a full meal and are like "I'm never eating again." But then, out comes a beautiful piece of cake. And, you said you were full, but not for dessert! It 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". That's what Dr. Rolls, a nutritional scientist, has been studying since the 1980s. Here is how her experiment went. She gave six people a giant plate of spaghetti and told them to eat until they were full. And then, for the second course, she gave them more. Then, she gave them ice cream. On average, after they said they were full on spaghetti, each person could eat just one more ounce of it in their second serving. But when she gave them ice cream, 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 the change in how much you like a food, how much you want to eat, as you're eating it. "I've just had enough of the food; I want something else" is really what sensory—specific satiety is.

And that natural ability has a purpose: it's meant to keep us healthy. It's going to help to guarantee that we're going to get the variety of nutrients that we need. However, it can backfire of course, because if we are presented with a variety of foods, it makes us extra likely to overeat.