Flipping over the food dish

My dog always knocks over her food dish, or flips it over. She usually tries to knock it over while eating. I'm not sure why she does this. I'm not sure who she is "protecting" it from, either. We do have another dog but she's been doing this before we took the other one in. Is it just instinct to hide her food so she can come back to it later if she wants? She's been doing it for quite some time. We usually just say, "No" and then she goes back to eating. Multiple times we've come home to a dish flipped over and left on the carpet.

Thoughts?