4 Tips to Help an Underweight Dog Gain Weight

If you notice your dog isn’t eating as much anymore or he’s getting too thin, this veterinary nutritionist has some advice for helping your pup get healthy again.
brendan-howard-headshot By Brendan Howard Medically Reviewed by Alicen Tracey, DVM Updated April 14, 2022 Medically Reviewed by Alicen Tracey, DVM Advertisement Pin FB More Tweet Email Send Text Message Print
dog eating from human's hand while sitting in the grass Credit: bnenin / Adobe Stock

When dog owners come for advice from veterinary nutritionist Lori Prantil, MPS, DVM, at VCA South Shore Weymouth, they usually want to help their dog lose weight, not pack on pounds. But weight gain does come up.

"I sometimes see weight loss with very active young dogs," Prantil says. Working dogs, like shepherds and sled dogs, can burn through thousands of calories in a day, and the amount of food each day may not be keeping up with their energetic lifestyle.

More often, medical conditions cause dogs to lose weight, and diets may need to be adjusted.

"Sometimes dog owners switch to a low-calorie food, like chicken and rice, if a dog isn't feeling well," Prantil says. If you don't switch back from a sick-dog diet, or the dog doesn't eat enough of the diet, your pup can lose muscle mass over time and struggle to maintain a healthy weight.

Reasons Why Your Dog May Be Underweight

There are plenty of potential causes for a dog to lose weight, including:

• Your dog is a picky eater. A dog might stop eating or eat less of a current diet for texture, flavor or other reasons.
• Your dog is stressed out. A dog's environment might change, with a pet owner's new baby, a newly adopted animal, a new home, or an owner who isn't around because of work reasons. This can cause changes in feeding or eating patterns.
• Your dog is sick. Diseases and other medical issues are a prime culprit for sudden weight loss. "Inflammatory bowel disease and kidney disease are possibilities," Prantil says.
• Your dog has mouth pain. Gum, tooth, or mouth pain can make eating hurt.

If you notice weight loss in your dog, a veterinarian can help walk through what you're feeding and how often to get an accurate calorie count. The veterinarian may calculate how many calories your pup needs by estimating their resting energy requirement. This number equals what your dog needs to stay alive, multiplied by 1.5 or more to figure out your dog's nutritional needs for active days. The two of you can experiment and develop a new nutrition plan.

RELATED: How Much Food Does My Dog Really Need?

4 Tips to Help Your Dog Gain Weight

"Every dog has different calorie needs," Prantil says. "They're like people. Some people can eat a whole pie and not gain a pound, and it seems like other people look at a pie and gain weight."

If you notice sudden weight loss in your dog, a trip to the veterinarian is a good first step. A veterinarian can check your dog's body condition, look for loss of muscle mass (not just fat) and find any underlying medical conditions.  

With a clean bill of health, you, your pooch, and your veterinarian are ready to start experimenting.

1. Offer More Frequent Meals

Other than with fast-growing puppies, Prantil never counsels dog owners to let dogs eat as much as they want all day long. She does suggest trying more frequent meals or leaving meals out for dogs to eat for longer periods. If a dog struggles to eat all their calories in one or two sittings, it can help to split up the day's calories in three or more meals over time.

RELATED: 3 DIY Ways to Prevent Gas and Bloat in Your Dog

2. Offer Different Treats (Maybe)

Even if your dog is eating a well-balanced, complete meal, either home-cooked or packaged, Prantil says it's OK to offer up to 10 percent of your dog's daily calories in safe human food or healthy dog treats.

"I don't like to give extra treats, even for weight gain, because dogs get 100 percent of their nutrients from their complete diet," she says. "I try not to add too many extra things to a diet, because we could unbalance the balanced nutrients."

While occasionally Prantil will add fat to a dog's diet for medical reasons, she says to steer clear of high-fat treats. Too much extra fat can cause pancreatitis.

(Sorry, athletes: Prantil doesn't recommend any particular weight gain supplements for dogs. No protein shakes for doggie bench-pressing in the gym quite yet.)

3. Switch From Dry to Wet or Back Again

If the issue for your underweight dog is texture or palatability, you might try switching from canned food to dry kibble, or vice versa. Some dogs need more variety than others.

This switch shouldn't be your first go-to, however, as new diets can upset dogs' stomachs. Prantil also says you might end up in a battle of constantly adjusting meals for a finicky pup.

"Some small dogs are picky eaters, and you can inadvertently encourage this if you top food with gravy, then with chicken or beef, and other things," she says. "Now the dog learns that they don't need to eat food if it doesn't have chicken on top. You could be constantly topping and rotating toppings."

4. Switch to a Higher-Calorie Food

Your veterinarian might decide a higher-calorie food is in order, and there are a number of packaged varieties, especially for large or active working dogs, on the market.If you have the time and the interest in offering a home-cooked meal (never raw, warns Prantil, because of risk of bacteria), you can start with a healthy diet built on BalanceIT.com. The website's AutoBalancer EZ for Healthy Adult Pets is restricted to healthy pets, so you could safely adjust homemade dog food for weight gain as long as it's with your veterinarian's guidance.