My father constantly has the uncontrollable urge to snack and it's getting annoying. How can we deal with this?

I'm not sure if it's the prednisone (15mg) or the dementia, but there are regular times throughout the day and night that my dad has a very strong urge to snack. He is not undernourished or hungry, he's a good weight and eats well at meal times. Anyway, these days it drives us crazy, he will eat almost anything if we put away all the snack items. Unless there is someone there to tell him he just had lunch, or to redirect him to reading or some other activity he will start rummaging thru the fridge and to the cabinets if he doesn't find anything there. If we leave out snacks, he just eats more and more. He could finish off three bags of chips if they were left out on the counter. Any suggestions? If not in how to change this behavior, in just how we can emotionally deal with this -- now getting annoying behavior.