I have two dogs one rescue and she could eat for England, when she can she eats hers, the cats and our other dog's food too, she cant go to sleep if there is any food left in the bowls, she just cant. We put it down to the fact she must have been really illtreated before we got her, though 4 years down the line she is still the same.
A pal calls her "barge ar*e" because she has filled out quite a bit since we got this poor skinny dog from the rescue people.