TLC's Resource: "Are Our Dogs Too Overweight and Therefore Unhealthy?"

A 9-point body condition scoring system has been developed for dogs. Consider the following five indicators on your dog and compare them to the body condition scores on the left.

Feel for your dog's ribs. You should be able to feel the ribs quite easily. There should be a slight amount of fat over them, but each rib should be distinct. If you can see the ribs, your dog is too thin. If you cannot feel them at all, your dog is very overweight.
Check the area near the base of your dog's tail. There should be a small amount of fat covering this area and it should feel smooth overall. If the bones protrude, your dog is too thin; if you cannot feel any bones at all, your dog is very overweight.
Feel other bony prominences on the dog's body such as the spine, shoulders, and hips. Again, you should be able to feel a small amount of fat over these areas. If these bones are easily felt or visible, your dog is too thin. If you cannot feel the bones beneath the layer of fat, your dog is obviously overweight.
look at your dog from above. (If your dog has long hair, it may be easier and more accurate to check your dog when he is wet-after a bath or a swim.) Your dog should have a definite waist behind the ribs. If the waist is extreme or if bony prominences are visible, your dog is too thin. If there is no waist, or worse yet, the area between the ribs and hips is wider than the hips or ribs, your dog is grossly overweight.
Look at your dog from the side. Dogs should have an abdominal tuck, i.e., the area behind the ribs should be smaller in diameter than the chest. This can vary a lot between breeds. Some dog breeds such as Irish Setters and Greyhounds, for instance, appear to have a much more distinct abdominal tuck, since they are so deep-chested. A dog who is too thin will have a very severe abdominal tuck. Overweight dogs will have no abdominal tuck.