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8 Reasons Why Your Dog Suddenly Doesn't Want to Eat

Analysis by Dr. Karen Shaw Becker

lack of appetite in dogs

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  • Healthy dogs are almost always healthy eaters, so a decrease in your pet’s appetite is very often a sign of an underlying condition
  • Make an appointment with your veterinarian if your dog’s appetite changes, and make an urgent appointment if the change is very sudden or dramatic
  • There are many potential causes for loss of appetite in dogs, including a painful condition, dental or gum disease, and stress
  • It’s very important that your veterinarian identifies and resolves the root cause of your dog’s lack of appetite rather than simply treating the symptom
  • Once the cause has been determined and treated, it’s important to calculate the number of calories your dog should consume each day to regain and maintain an ideal weight

A healthy family dog who is underweight is a rarity these days. The vast majority of dogs with a weight problem need to lose rather than gain weight. That’s why if your dog is dropping pounds (or ounces in the case of tiny breeds), it’s usually tied to a change in appetite.

And as most experienced pet parents know, a change in a dog’s eating habits — especially a loss of appetite — is a red flag.

Your Dog’s Appetite Is an Indicator of His Overall Health

If your dog refuses to eat for longer than a day or two, especially if there are other symptoms, or if there’s a sudden noticeable reduction in his food intake, it’s important to see your veterinarian right away. If the decrease is gradual, it’s just as important to get him checked out, but it’s not as urgent a situation as a sudden, dramatic change.

It will be your veterinarian’s job to search carefully and thoroughly for the underlying cause of your pet’s loss of interest in eating, because there’s almost always a cause. His appetite won’t improve long-term until the root cause of the problem — not just the symptom — is identified and addressed.

Appetite stimulants prescribed by your veterinarian can be useful in the short-term, but they don’t address the underlying problem of inappetence. They may for a time successfully treat the symptom (refusal to eat), but not the cause.

When it comes to treating a dog who won’t eat, there’s no one-size-fits-all approach. Your veterinarian must do a thorough physical exam and diagnostic workup, and investigate metabolic changes such as hypertension, blood potassium levels, anemia, or vomiting. He or she should also consider any medications or supplements your pet is taking to rule those out as a cause.

You’ll also want to fill your vet in on any changes that have occurred in your dog’s environment or daily routine that might be causing him stress.

The cause of your dog’s disinterest in eating will determine an appropriate treatment approach. If there’s an underlying disorder that can be successfully treated or managed, his appetite should return to normal as the condition resolves.

Causes for Loss of Appetite in Dogs

When a dog with a normally good appetite loses interest in food, it’s a symptom of an underlying problem. Potential triggers include:

Dental or gum disease — Sometimes a problem in your pet’s mouth can make eating a painful experience. This can be a broken or loose tooth, severe gum disease, or an oral tumor.

Pain — A painful condition anywhere in the body, and especially in the GI tract or mouth, can cause your dog to eat less or refuse to eat.

Illness — A dog who feels sick will often show little or no interest in eating. Sometimes it’s just a passing gastrointestinal (GI) disturbance; other times it’s much more serious, such as a systemic infection, liver or kidney disease, or cancer.

Nausea — While relatively uncommon in dogs, nausea can certainly put your pet off her food. Unless there’s an underlying illness, nausea most often accompanies car travel.

Recent vaccination — Loss of appetite can be an immediate adverse effect of vaccination.

Stress — If your dog is feeling stressed for some reason, he may turn away from his food bowl. For example, some dogs don’t have much appetite when they’re in an unfamiliar place, their favorite human is away from home, or when there are other pets around at mealtime.

Obtundation — This condition is a lack of alertness more pronounced than lethargy and is usually the result of an underlying medical condition such as hypercalcemia, metabolic disease or trauma. 

Food aversion or pickiness — Food aversion can occur if you make a sudden change to your dog’s diet. It’s almost never a good idea to do this quickly because it can cause diarrhea. If you want or need to change the diet you’re feeding, do it gradually by mixing the new food in with the old food in a slow transition.

Some dogs refuse to eat certain foods for reasons that may or may not make sense. And some are simply notoriously picky eaters who often require special menus or lots of coaxing.

In addition, over the years I’ve known many dogs on processed diets who were considered fussy eaters, or who spent as much time playing with their food as eating it. When their owners gradually transitioned them from a kibble or feed-grade canned diet to raw or gently cooked fresh food (more about this shortly), the weird eating habits disappeared.

Many animals just don’t like the food they are being offered, so offering a completely new type of food may remedy the problem.

Needless to say, there are many other potential reasons a pet stops eating: GI foreign bodies, exposure to or consumption of toxins, and dozens more. Your veterinarian will recommend diagnostics based on your dog’s physical exam findings.

It’s also important to note that some breeds maintain their weight beautifully while only eating once a day or every few days. This is a completely natural and healthy eating pattern for many dogs. This article is about animals that are losing weight from not eating enough, which signals a problem.

Click here to find out Dr. Becker's top tips against seasonal pet allergiesClick here to find out Dr. Becker's top tips against seasonal pet allergies

How to Feed Your Dog for Healthy Weight Gain and Maintenance

Once the underlying cause for your dog’s loss of interest in food has been identified and treatment, if necessary, is underway, I strongly encourage you to review the quality of the diet you feed her and see where it falls on my list of best-to-worst pet foods. The food you offer will play a foundational role in helping your dog regain the weight she’s lost, maintain her interest in food, and improve her health and overall vitality.

As always, I recommend a nutritionally optimal, diverse, species-specific fresh food diet containing ample amounts of healthy fats. For animals who are underweight, feeding a calorically dense diet (where approximately half of the calories come from fat and half from protein) is an excellent way to help add back muscle mass.

Decide what your dog’s ideal weight should be (with input from your veterinarian, if necessary), and calculate the calories she’ll need to consume each day using the following formula:

Daily calories = Body weight (kg) x 30 + 70

Let’s say your dog is currently 54 pounds and her ideal weight is 60 pounds. Her ideal weight — not her current weight — is the one you’ll want to plug into the formula. First, convert the ideal weight from pounds to kilograms. One kilogram = 2.2 pounds, so divide her ideal weight in pounds (60) by 2.2. Her ideal weight in kilograms is 27.3. Now the formula looks like this:

Daily calories = 27.3 (kg) x 30 + 70

And finally, it looks like this:

Daily calories = 889

If your dog eats 889 calories a day, she’ll regain and maintain her ideal 60-pound weight as long as her daily activity level remains the same. If she starts getting more strenuous exercise each day (which benefits almost any dog, by the way), you may need to increase her calorie intake to account for an increased activity level.

If your dog is highly active you sometimes have to dramatically increase the number of calories she consumes on a daily basis. Some dogs, such as young German Shorthair Pointers, may need two or three times the number of calories as a lazy dog at the same body weight.

But if for some reason your dog is suddenly not getting the workout she’s accustomed to, it may be a good idea to reduce her daily calories a bit until she’s back exercising at her former level.

It’s important to routinely monitor your dog’s body for signs of weight loss or gain, and weigh her regularly as well, either at home or at a veterinary clinic if she’s too large to weigh on a bathroom scale. If her weight starts to creep in either direction, adjust those daily calories up or down.

If she drops below her ideal weight due to increased physical activity, you may need to increase her daily calorie intake as well. The above formula does not take into account dogs burning lots of calories if they are working hard for many hours a day (because most dogs simply aren’t).

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