You push back from the table after Christmas lunch, full from an excellent feast. You really couldn’t manage another bite – except, perhaps, a little bit of pudding. Somehow, no matter how much you’ve eaten, there always seems to be room for dessert. Why? What is it about something sweet that tempts us into “oh, go on then”?

The Japanese capture this perfectly with the word betsubara, meaning “separate stomach”. Anatomically speaking, there is no extra compartment, yet the sensation of still having space for pudding is widespread enough to deserve a scientific explanation.

Far from being imaginary, the feeling reflects a series of physiological and psychological processes that together make dessert uniquely appealing, even when the main course has felt like the limit.

A good place to start is with the stomach itself. Many people picture it as a fixed-size bag that fills steadily until it can take no more, as though another mouthful would cause it to overflow.

In reality, the stomach is designed to stretch and adapt. As we begin to eat, it undergoes

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