Spencer, I'd probably suggest Blue Buffalo puppy food. Puppy food has a higher fat content than adult dog food. Just like you are to give human babies whole milk until they reach 2 years old and then switch to skim. They need the fat for the brain development so anything for babies has it. So what I'm saying is that if you want to put weight on with just food and not adding something in, switch to puppy food for a while until you start to see weight appearing on the dog.