I feel your pain, we have a large black lab (suppose to be pure lab but is the size of a small great dane) and he will eat anything in any amount. He can eat two heaping bowls though he is only suppose to have one (6 cups each) of Iams and I still catch him licking the scratch feed off the ground, trying to gobble up any corn we throw for the chickens before they get it and he will eat the whole feeder of chicken feed as well as all the eggs if he can get into the garage, I threw some old lettuce out the other day for the wild rabbits and found him a few minutes later with the head of lettuce in his mouth trying to hide it because our other dog thought he might have something good. She on the other hand will only eat dog food, and prefers old roy to anything else ( I know, crap food) we mix it with the iams for her so she will eat it and still fight with her to eat a bowl of it. If you find a solution to your dogs apatite let me know. Apollo could easily finish off a bag of dog food in a week if you left it down for him. We caught him knocking the lid off our  container we store the dog food in, he ate half of it before we caught him, and the farts this dog has, OMG, he can clear a room!
Good luck