If that happens, I make a note of what I was eating (or doing, if it was exercise) because my food is usually planned in such a way that I shouldn't feel hungry.

But, because of my own PCOS problems, I know that too many carbs can trigger hunger before my next snack/meal so I take a look at what I have been eating, because maybe it's too many carbs without enough protein.

Protein and fat keep me satiated, even in small amounts. I'll fix what went wrong and usually go for a protein to keep me until my next snack/meal.