Many owners fight the battle of the bulge with their dogs. While your dog carrying too much weight can cause health problems, did you know that it’s also vital that a dog isn’t underweight? Ultimately, being underweight is not healthy for your dog, as it can compromise your pooch’s long-term health and negatively affect quality of life. For your dog’s system to run effectively, your pup needs to fall within the ideal weight range for its breed and age.

Long-term underweight in dogs can lead to a slew of health issues, such as a weakened immune system, susceptibility to infections, slow wound healing, reduced bone density, muscle loss, hair loss, and a shortened lifespan. In this post, we’re taking a look at some of the reasons your dog might be underweight, plus how to get them to a healthier weight so that they’ll thrive. 

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5 Reasons Your Dog Might Be Underweight or Undernourished

There are a variety of reasons your dog might be underweight. Here are some of the most common reasons.

Insufficient diet or underfeeding

Just like people, a dog that isn’t fed or doesn’t eat enough is going to become too thin. This may be because your portion sizes are too light, or the caloric and nutrient-density of the food aren’t high enough. If your pup’s diet is lacking, your furry friend will gradually lose weight. It may then be difficult for your pooch to gain the weight back.

Illness and Disease

One of the most worrisome reasons for your pooch’s weight loss is the presence of an illness or disease. A common disease that can lead to weight loss is Type 1 Diabetes. Other diseases that may be at the root of your pooch’s underweight status include pulmonary conditions, abdominal disease, cancer, and thyroid disease. 

Parasites are another illness that dogs contract that leads to weight loss. Your vet can test for any diseases to determine the root of the problem.

Teeth conditions

Periodontal disease, including abscessed teeth and inflammation of the gums, is a common problem with dogs, especially as they age. According to the American Veterinary Medical Association, it is the most common dental condition in canines. 

Sticking to a dental hygiene regimen for your pup from an early age is key. There are a lot of teeth cleaning products on the market, including toothbrushes designed specifically for dogs and dog-safe toothpaste. If their dental hygiene has deteriorated, your vet might recommend having a thorough in-office cleaning, which typically requires sedating your dog.

A side effect of medications

If your dog is taking medications, certain ones are known to cause the side effect of loss of appetite, which will inevitably cause your pup to lose weight. Talk with your veterinarian about alternative medications that don’t have this side effect or other ways you can provide them with the nutrients they need.


As a dog ages, it’s normal for them to experience a reduced appetite. Loss of appetite and weight loss resulting from age may occur gradually over time, so having annual (at least) check-ins with your vet can help you keep an eye out if they’ve lost a significant amount of weight. 

4 Tips for How to Put Weight on a Dog

Once you’ve determined the cause (or causes) of your dog’s weight loss, it’s time to employ some strategies to get your pup to gain weight. Here are a few methods to get you started. 

1. Sufficient feeding schedule and serving sizes

Make sure that you are feeding your pup a sufficient amount of food. Serving sizes are highly specific for every dog based on their age, current weight, breed, activity level, and wellness goals (e.g. an extra shiny coat). It’s an easy thing to get wrong. And dogs aren’t always the most reliable source of truth regarding how much they should eat. Some dogs will eat everything you put in front of them, while others are pickers and might be more stingy about how much they eat at a given time.

Puppo helps pet parents figure out the serving sizes your dog needs to live their best life based on the unique qualities of your pup. Take our quiz to figure out if you’re feeding your dog the right amount of food they need. 

2. High-calorie dog food or supplements

Begin feeding your dog higher-calorie dog food compared to what you’re currently providing. When you make the change to a more nutrient-dense food for your pup’s wellbeing, you’ll want to be sure you make the transition gradually

Your vet might also recommend supplements, which can help increase your dogs appetite.

3. Provide snacks in between meals

Supplementing your pup’s diet with snacks is another good way to sneak in additional calories that can lead to weight gain. Look for supplemental foods made from meat sources that are high in protein and contain some fat. Such treats shouldn’t replace meals but are a good addition when extra pounds are needed. 

4. Muscle gain through exercise

Since muscle weighs more than fat, ensuring that your dog gets plenty of exercise will lead to weight gain. Exercise is a healthy activity that is good for your pet’s wellbeing and longevity. This can also increase your pup’s appetite. On days they get extra movement, make sure they’re getting enough food to fuel their extra-exerted energy.

Being underweight is an unhealthy place for your pup to be, but the tactics mentioned above can help your pup enter a healthier weight range.

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