dessert stomach; room for dessert
Humorous or colloquial expression for having a separate appetite for sweets even when full from a meal.
Even when I'm full, I can eat cake because I have a separate stomach for dessert.
彼はいつも「別腹」と言って、食後にアイスを食べる。
He always says 'dessert stomach' and eats ice cream after a meal.
Compound of 別 (separate) and 腹 (stomach). The idea is that there is a separate stomach for dessert, even when the main stomach is full.