Do Pokemon get hungry while in their Pokeballs?

It's an odd subject, but a subject nonetheless. I've noticed in the old episodes of the Pokemon anime, none of the pokemon ate anything with regularity. They seemed like creatures who never ever get hungry. In later episodes, the subject is being touched on with berries, poffins, pokeblocks, etc.

So, I was wondering, do they? I've always imagined that when they're called into the pokeballs they're transformed from matter to energy thereby eliminating such a requirement. But with Dawn, Ash and Brock cooking stuff up more often and giving their Pokemon berries, I'm not sure what to think anymore...

Thoughts?