My Dog Has Been Losing Weight
Most dog owners spend a significant amount of time worrying about ways to prevent their dogs from gaining weight. The opposite problem is rarely the case. When a dog does appear to be losing weight inexplicably, it is always cause for concern.
The first step toward a resolution is to go over your dog's eating and exercise schedule. Question all members of the family about their responsibilities related to the dog's care and feeding. Go as far as making a chart that quantifies amounts of food offered and actually consumed, and duration of and exertion during the various walks the dog is taken on. Not until the logic of this part of your dog's daily routine has been established should you move on to further investigation.
What to Look For
Weight loss is weight loss. When it represents a threat to your dog's health, however, it is much more of a concern. Of course, any time significant weight loss is mentioned, a thorough physical exam is called for.
For your current purposes, though, let's focus on your dog's immediate issues. Start evaluating your dog as a whole. Analyze his levels of energy and enthusiasm. Check his fur to see if it is sparse, coarse, or dull. Look for any loss of muscle mass. If you observe such a loss, see if it occurred in a symmetric fashion or if it is limited to certain parts of his anatomy. Check for evidence of protruding bones, especially the ridges of his skull, his shoulder blades, spinal vertebrae, ribs, and hips.
What to Do
Now go through the following questions to figure out what to do next: