What Causes Weight Loss in Cats?

CatChannel's veterinary expert, Arnold Plotnick, DVM, offers his insight on what can cause weight loss in otherwise healthy cats.

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Q: I have a 9-year-old gray and white housecat who has weighed 16 pounds for years. In the last few months he has lost 4 pounds and doesn't seem to eat as much. I have two other cats that are fine.

My veterinarian has tried everything: medications for parasites, blood work for diabetes, leukemia, kidney function and more. He tried arthritis medications and antibiotics, he did a chest X-ray and performed multiple physical exams. Everything is normal with the exception of a slightly elevated protein. He’s had no behavior changes; he still runs, jumps, purrs and plays. What is causing my cat’s weight loss?

A: Weight loss and a mediocre appetite can be a frustrating thing to diagnose. Diabetes, hyperthyroidism, and chronic renal failure are three illnesses that result in weight loss and are commonly seen in older cats. However, cats with hyperthyroidism and diabetes tend to have a strong appetite. Cats with renal failure tend to have a poor appetite. All three of these disorders are diagnosed easily via routine bloodwork. It appears that your cat does not have any of these illnesses, according to the test results you’ve described.

In my experience, cats that experience weight loss and poor appetite, with very few other clinical signs, often have inflammatory bowel disease (IBD), a condition in which inflammatory cells infiltrate the intestinal tract. The four most common signs seen with IBD are vomiting, diarrhea, weight loss and poor appetite. These signs can occur solely, or in any combination. Vomiting and diarrhea are commonly seen as symptoms of gastrointestinal disease, and most veterinarians will explore the possibility of a gastrointestinal disorder when cats are vomiting and/or have diarrhea. Poor appetite and weight loss, however, are very non-specific signs.

If bloodwork and X-rays do not reveal any obvious abnormalities, many veterinarians doubt that a gastrointestinal disorder might be likely still. An abdominal ultrasound is a relatively non-invasive method of evaluating the gastrointestinal tract. It might give a hint that there’s a gastrointestinal disorder, but a definitive diagnosis of IBD is obtained through a gastrointestinal tract biopsy. Exploratory surgeries and biopsies, or endoscopies can offer a diagnosis. An endoscopy is less invasive and is the preferred method, in my opinion. I’ve diagnosed many cases of IBD in cats with vague clinical signs, such as weight loss, poor appetite or both. Fortunately, IBD usually responds to appropriate therapy and many cats do well for years on medication and special diets.

Arnold Plotnick, DVM

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Reader Comments

Janet    Bethlehem, PA

6/19/2011 7:39:08 AM

good article, thanks very much

Lisa    Rochester, NY

2/11/2011 4:44:32 AM

My 10 yr old female has been losing weight and she had been very overweight to begin with. She still has a good appetite and is acting normally, but I guess I should get her checked out for one of those disorders mentioned in this article. Thanks.

Copper    Chandler, AZ

2/7/2010 7:50:44 AM

I have a 5 year neutered male cat who, despite an increase in appetite and water intake is losing weight. What might be the cause?

Janet    Bethlehem, PA

10/10/2009 7:19:56 AM

good article thank you

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