No one likes the look of a skinny, underweight dog. Putting weight on your dog, however, can be a challenge. If you're lucky, all it will take is increasing the amount you feed him, but more likely, getting your pup to a healthy weight will require several lifestyle changes.
Measure His Food
Your dog may not be getting enough food. The recommendations on the back of the bag are just that -- recommendations. Your dog may need more if he is active, coming back from an illness or young. Increase the amount of food you offer and don't eyeball the amount -- use a measuring cup. You also need to know how much your dog is eating before visiting the vet, as this will likely be one of the first questions your vet asks, and you want to know the actual amount, not an estimate.
Visit the Vet
There are many medical reasons why your dog may not be able to maintain a healthy weight. Illnesses such as diabetes, heart disease and cancer can all lead to a loss of appetite and weight loss. If your dog has internal parasites he won't be able to absorb nutrients properly in food, which will lead to weight loss. Finally, dental problems can cause pain, which may make your pup reluctant to eat.
Change His Diet
Feed a quality food and consider switching to a different formula. If you are feeding a formula for mature adult dogs, talk to your vet about switching to a formula designed for puppies or active dogs. These foods have more calories per cup than foods designed for maintaining weight in average adult dogs. When switching food, make the change gradually over the course of a week to prevent the switch from upsetting your dog's stomach.
Tempt His Appetite
While some dogs are seemingly bottomless pits, others don't seem to have as much of an appetite. If you are having trouble getting your dog to eat more, there are several things you can do to tempt his appetite. If you feed canned food, warm it up slightly before serving it. If you feed dry food, add a little warm water to warm and soften the food. If you normally set your dog's food out once or twice a day, try feeding him free choice. If he is used to eating free choice, switch it up so he gets two or three meals a day. The change may be just what he needs to eat a little more.