Preparing for Hibernation

I think my cats are preparing for hibernation. Since we moved I've noticed they both have been eating, eating, and eating some more. I pour two cups of food in the morning and by night it's all gone. They're taken to begging for canned food. I just feed them more. I'm not alarmed because one (Cookie) I've notice has gotten thinner since he turned 15 and the other (Piddles-Gayle) is a little chunk with a generous rump. This happened when we moved into our new house. Hmmm...

Possible theories:

1. Going up and down the stairs wears them out and they eat more..
2. They're eating for two, but they're both males..
3. They dreamed in their lil cat dreams that we were out of food...once
4. They think we're not coming back when we leave in the morning..
5. They're preparing for battle..
6. They're going into hibernation soon