There may be a variety of reasons why a dog scarfs down its food in record time. If there is no medical explanation and you don't speak canine, you may never know why your dog choose to behave this way. It is important to slow down a dog's eating, no matter the cause. Eating too fast can be a choking hazard as well as lead to obesity.
Take the dog to the veterinarian for a full exam including a fecal for parasites (i.e., worms). The dog may be eating fast due to a medical problem. If parasites are living within your pet, they are stealing the nutrients from the dog food so the dog is constantly hungry.2
Purchase high quality dog food from the veterinary office or a pet food store. Quality dog food may seem more expensive, but the dog actually eats less and feels full faster. Feed only the recommended daily amount, no more. Some examples of quality dog food include Pinnacle, Cannidae, Diamond Naturals, Merrick and Eagle Pack. There are many available so ask your veterinarian for advice.3
The easiest way to slow down a dog's eating is to simply make the food less accessible. A free, yet messy fix to this problem is to spread the dog food out on a cookie sheet with low edges. This way your pet must chase the food, making it nearly impossible to pick up more than a few pieces at a time.4
There are also a variety of slow-feeder dog bowls on the market. Costs and features vary widely, so do some shopping before you buy. One of the cheapest bowls that I have had success with is a stainless steal puppy feeder made by ProSelect. Also worth a try is the Brake-fast dog food bowl available on Amazon. The idea with all of these slow-feeder bowls is the same, to make it impossible for your pet to get more than a few pieces of food in one mouthful.5
Stay in the room with the dog while it is eating. Praise your pet after it has slowed its eating habits and do not give treats or more food.