In many ways, it's easier to buy healthy food for yourself than your dog. You should mostly stick to the produce aisle, adding whole grains, some fish, and a bit of meat to the cart. But for Fido? You have to read the labels on dozens of nearly identical bags — and sort through the marketing, confusing ingredient lists, and contradictory statements. We talked to the experts about how to see through the hype and get the best food for your dog.