2. Sudden weight loss

Sudden weight loss is always a cause for concern. If your dog is not on a diet but keeps losing weight, it might be a clear sign that he suffers from some illness. Firstly, you might notice a loss of appetite. Your dog is not jumping at you anymore when you open that bag of chips. You fill his bowl with food, and he is not even eating half of it.

One thing that you need to know is that the weight loss caused by cancer is different from starvation. If a dog is starving, he will first lose fatty tissue. However, in the case of cancer cachexia, the dog will lose fatty tissue as well as muscular mass at the same time. 

If you notice that your canine friend is not eating as he used to and is losing weight, take him to the vet immediately.