How To Fatten Up A Dog & Encourage Healthy Weight Gain (Hint: Finding The Underlying Cause Is Key.)

Most dog owners struggle with helping their dog lose weight… rather than gain weight.

But it may be necessary to put your dog on a weight gain diet, in some cases.

First, it’s important to determine what’s caused weight loss in the first place.

Medical Conditions That Can Cause Weight Loss In Dogs

It’s normal for any pet’s weight to fluctuate a little bit throughout the year.

For example, some dogs love warm weather and exercise more during the summer months than the winter, burning more calories during this time and causing weight loss.

The opposite is typically true of “Northern breeds”, like Malamutes and Huskies, who love to spend their days in the snow.

Medically, weight loss becomes a concern when a dog loses 10% or more of their average adult weight… unless they’ve been put on a diet and the weight loss is intentional.

Medical conditions that can cause unintentional weight loss include:

Internal Parasites

There are a number of internal parasites that can infect a dog.

The most common include:

  • Roundworms;
  • Whipworms;
  • Tapeworms;
  • Hookworms;
  • Giardia;
  • Heartworms.

Although many dogs are regularly dewormed each month, not all dewormers target all potential internal parasites.

Dogs with a serious infection will typically show symptoms such as weight loss, diarrhea, vomiting, and lethargy. Worms or worm segments may be visible in the vomit or stool.

Your veterinarian will need to perform diagnostic testing to determine which type of internal parasite your dog has. Then they can prescribe the correct deworming medication.

Inflammatory Bowel Disease (IBD)

Researchers continue to study IBD in dogs, hoping to identify the underlying cause of this condition which can result in weight loss.

Although there are no definitive answers, it is believed that there are two main causes of IBD:

● bacterial overgrowth;
● a reaction to a protein in the dog’s food.

Whatever the cause, the result in inflammation in the GI tract, most commonly in the stomach and/or intestines. This inflammation interferes with the body’s ability to absorb nutrients and as a result, a dog with IBD will experience periods of vomiting, diarrhea, and sometimes weight loss.

If your veterinarian suspects that your dog has IBD, they may want to confirm this diagnosis through tissue biopsies obtained from the GI tract.

IBD is commonly treated through a combination of diet changes, antibiotics, and steroids.

Addison’s Disease

Addison’s Disease is the common name for a condition called hypoadrenocorticism.

Basically, this is a hormone disorder caused by the decreased production of cortisol and aldosterone by the adrenal glands.

Dogs with Addison’s are often difficult to diagnose as symptoms can come and go.

Symptoms may include any combination of lethargy, tremors, increased thirst and urination, vomiting, diarrhea, and weight loss.

If the disorder is allowed to progress, the dog may have what is called an Addisonian Crisis. Dogs in this crisis will often have severe vomiting and diarrhea followed by a collapse. Immediate treatment is needed to stabilize them.

Addison’s can be treated with regular injections of a drug called Percorten-V.

Kidney Disease

Chronic kidney disease can cause muscle wasting and ultimately weight loss.


Although very rarely seen in dogs, hyperthyroidism can occur.

When the thyroid overproduces a hormone called thyroxine, this causes weight loss because thyroxine stimulates the metabolism.

Common signs of hyperthyroidism aside from weight loss include vomiting, diarrhea, increased thirst and urination, rapid breathing, hyperactivity, and a newly diagnosed heart murmur.

During an exam, your veterinarian may actually be able to feel that the thyroid gland is enlarged.

Your veterinarian may recommend prescription medications, the removal of the thyroid gland, or radioactive iodine treatments as a treatment for this condition.


When the pancreas fails to produce the correct amounts of insulin, cells are unable to take in glucose, a main source of energy.

This results in increased blood sugar and without glucose, the cells instead break down fat and protein the body as alternative sources of energy.

This breakdown causes weight loss.

Without treatment, a dog will go into Diabetic Ketoacidosis (DKA), a condition that is life-threatening and requires immediate medical attention.

Stress & Anxiety

When a dog is stressed or anxious, this can cause them to lose their appetite.

It’s important to always monitor your dog’s food intake to ensure that they are eating properly.

If you suspect that your dog is stressed or anxious, it’s important to identify what is upsetting them. Then through training and behavior modification, you can help your dog overcome the issue.


The world isn’t always a kind place and many rescue dogs sustain serious weight loss simply because the person abusing them starved them.

It’s barbaric and horrific and those who intentionally starve a dog should be punished.

If you’ve rescued a dog who was abused the weight loss may not indicate anything other than the loss of regular meals.

With time, love, and food, abused dogs should quickly and naturally gain weight.

How To Fatten Up A Dog & Encourage Healthy Weight Gain (Hint: Finding The Underlying Cause Is Key.) 3

How Can I Help My Dog Gain Weight?

After you’ve identified the cause of your dog’s weight loss you may want to help them gain some of that weight back.

The most important step is to discuss their diet with their veterinarian.

For example, dogs with kidney disease need to be on a very specific diet, one low in sodium, protein, and phosphates. Additionally, dogs with GI conditions like IBD may also need to be on a special diet that is low in fat, prescribed by a veterinarian.

Many dog foods that are designed to help a healthy dog gain weight are NOT appropriate for dogs with these medical conditions and should be avoided as they can actually make the dog sicker.

Always follow your veterinarian’s recommendations regarding diet.

If, however, you have a dog who has been cleared to eat any type of dog food, you might want to consider one of the following high-calorie diets:

The Best Dog Foods For Weight Gain

Last update on 2023-06-02 / Images from Amazon Product Advertising API

This food is high in protein, high in fat, and is incredibly nutrient-dense. Made from salmon and tuna, your dog will love the taste.

The protein content will help them to build strong muscles and the extra omega-3s provided by a fish-based diet will promote healthy skin and fur.

Last update on 2023-05-12 / Images from Amazon Product Advertising API

This food has been developed to help meet the nutritional and energy needs of working dogs who burn more calories than the average pet. This totally balanced diet is also high in protein and fat.

Last update on 2023-05-07 / Images from Amazon Product Advertising API

Another high fat and high protein dry dog food, Adirondack is a great choice for dogs that need to gain a little weight. The food is made from chicken and brown rice so picky dogs who only eat poultry will fall in love!

It’s important to remember that your dog won’t need a high-calorie diet forever.

Once any medical issues have been addressed and the lost weight has been regained, you might want to switch them back to a normal caloric intake so they don’t continue to gain and become obese.

If you are unsure about what an optimum healthy weight is for your dog, discuss this with your veterinarian. They can provide you with a target weight based on your dog’s size and build.