Dog Acts Like Shes Starving

So I adopted my dog from the pound 5 years ago and shes amazing. One weird thing is she always acts like shes starving to death (shes a few lbs over weight in fact). Everything is food. Throw a ball, she runs over, sees its not a treat ball. She sits and stares at me while whining all the time; ill try to take her outside and she doesnt want to go, I throw the ball a few times doesnt want any part of it, try and pet her but petting her would interfere with her ability to get food so she bends away and the vet said shes healthy. I have no idea what to do, anyone have any ideas?

Thanks so much!