I would not think they would be any more hungry than they normally are - though the more they exersize the more they eat is true. (just not noticable changes - too small to see!) Goldfish are ALWAYS hungry though!
Now that they have more space to be active, they are dancing for food and doing what healthy fish do - swiming and playing in the tank. That "play" involves doing what bottom feeders naturally do -they upend every thing they can looking for food. That means plants, rocks and deco will be moved around as they see fit.
Any plant that is even slightly interesting will be nibbled. That is the nature of the fish. I have never been able to keep live plants in my goldie tanks. They rip them from the bottom, race all over the tank playing keep away with each other and shred the plants. The shred-ate is then eaten with much gusto - producing large volumes of green waste I have to vaucumn up!
I have even made the plant books required reading for all the fish - showing them the pages that state that the various plants are not edible or of interest to goldfish. They read it, laugh and go back to plant LaCrosse games.
You may find you cannot keep plants in a tank of happy healthy goldfish atheletes!