Eating and drinking takes away one's appetite.

Hunger fades as a person consumes food and drink. The proverb treats a loss of appetite as the expected result of satisfying it.

It can also make a practical point about timing: someone who fills up beforehand may have little interest in a meal offered later.

Use it when someone eats or drinks before a planned meal and then finds the meal less appealing. It can be a light, matter-of-fact response to a diminished appetite.