Causes Of Extreme Weight Loss In Dogs. If your dog is older and is suddenly losing weight, this may be an early sign that they have cancer. Insufficient caloric intake relative to energy expended.
Because 2/3 of your pet's body is water, sudden weight loss may be caused by dehydration. This may be caused by high energy demands, poor quality food, or a number of health issues. It causes symptoms such as weight loss, vomiting, weakness, drinking and peeing.
