A dog who is undernurished should be feed a high quality food such as, Solid Gold Just a Wee Bit Adult Dog Food to help ensure that they are getting the nutritents that they need. In many cases, dogs and cats, can get undernourished for a variety of reasons. To help combat this issue, we recommend that you provide your dog with a high calorie supplement, such as our PSCPets High Calorie Gel, which not only provides that calories that your dog needs, but also a wide variety of vitamins and minerals. As always, we recommend that you check with your vet to see if there is an underlying cause to your dog's undernourishment that needs addressed medically.