2. Loss of Appetite
A loss in appetite is often accompanied by a change in the metabolism of the dog. The metabolism speeds up, and the appetite is diminished at the same time. This will cause the dog to lose weight at a rapid pace. Furthermore, after loosing their appetite for some time, dogs will lose their energy and become lethargic. If your dog is experiencing a loss of appetite that isn’t due to an infection or a parasite, it may be due to cancer.