It’s common behavior but there are several reasons. Unlike their owners, who can eat at their leisure, dogs have to wait for us. By the time we get around to it, they can be quite hungry, depending on how long it’s been since their last meal. Hunger leads to greedy eating. If you have multiple dogs, it might be competition. The dog may have a medical issue. Anything from a parasite to improper digestion and lack of proper nutrients can influence the behavior.