Weight loss in cats

What if you suddenly notice your cat is losing weight? Is it acceptable that your pet who was once fat now looks slender and sheik? When does weight loss in cats turn serious?

Weight loss in cats can be abrupt or chronic. Chronic cases can go unnoticed for weeks or months. Cats are sensitive creatures and may lose weight over seemingly minor events such as stress.

Other times, weight loss indicates a serious illness and requires diagnosis and intervention. Frequently, weight loss becomes overshadowed by other symptoms.

We go over when weight loss in cats is a concern and what specific problems are commonly to blame. We will briefly cover some healthy ways that your cat can lose weight if she is too heavy. Finally, we give objective ways to tell whether your cat is gaining or losing too much weight.

What is weight loss in a cat?

Many house cats are relatively sedentary and perhaps a little overweight making fluctuations in weight unnoticeable. Moreover, you may be thrilled that your cat is finally losing some of that belly fat your veterinarian is always talking about. Pets that go in and out of the house may lose weight; It escapes notice because of a heavy fur coat.

Know when enough is enough

If your cat is losing weight and you do not have her on a diet, you should immediately take notice. While weight loss in cats is not always serious, you must start thinking about it analytically.

  • Start tracking your cat’s weight with a scale; Schedule regular weekly weight checks with your veterinarian if necessary.
  • Monitor your cat’s appetite. Did he stop eating? Is he eating less than usual? Is he perhaps eating more than normal? If your cat feeds free choice, you may not immediately notice changes in appetite.
  • Have you experienced any major changes such as moving, having a baby, or other events that might be stressful for your kitty?
  • Has your cat’s behavior changed? Does he seem more lethargic, dull, or hyper? Has his voice changed?

Once you begin monitoring your pet, you can assess if your cat is displaying symptoms of a disease process. You can also objectively determine how much weight your cat is losing and how significant or serious it is.

A twenty percent loss in body mass may not be much for a huge Maine Coon. On the other hand, if your diminutive six-pound Devon Rex loses ten percent of his weight, it might be devastating.

Develop skills to assess body condition

Even without immediate access to a scale, you can become adept at checking your cat’s body condition score. If you think your cat is losing too much weight, you can confirm or deny it. Maybe you want your cat to slim down. You can assess her progress without always having to weigh her.

A scale gives you an objective way to measure weight loss, but body condition allows you to be aware of subtle changes more quickly.

Find a quiet place to evaluate your cat. Perform all steps systematically although they do not have to be in a particular order.

  1. Look down at your cat – This is the best way to assess your cat’s waist
  2. Look at your cat from the side
  3. Pet your cat – Feel for the prominence of ribs and spine
  4. Get a feel for how much muscle and fat your cat has and make a mental note

The ideal body condition of a cat is straightforward once you conduct your assessment.

  • The waist is obvious but not extreme – Slight hourglass shape or subtle indentation from the ribs to where abdomen prepares to join hips
  • Slight abdominal tuck – Abdomen rises minimally from the end of ribs to the hips; Nothing approaching the abdominal tuck on some deep-chested dogs
  • Spine and pelvic bones are not easily visualized, even on a hairless cat
  • Ribs should be easy to feel under a thin layer of muscle but never visible, even on short-haired cats
  • A small amount of abdominal fat is ideal

If your cat’s ribs are visible or seem prominent as you pass your hands down your cat’s sides, she is too thin. If you can see every vertebra or the hip bones stick out too much, your cat may be experiencing severe weight loss.

Experts use a standard numerical grading system. According to the VCA, there are two acceptable scoring systems. One uses nine classifications and the other only five.

Nine Point Body Score System

  • BS1 – Emaciated, severely underweight
  • BS2 – Extremely thin
  • BS3 – Too thin
  • BS4 – Underweight; some sources rate BS4/9 as ideal, others put ideal as starting at BS4.5/9
  • BS5 – Ideal
  • BS6 – Overweight
  • BS7 – Heavy
  • BS8 – Obese
  • BS9 – Severe obesity

The five-point system is very similar with a smaller range for the categories. As cats become underweight, their ribs become more easily felt and then increasingly visible. Likewise, the spine and pelvic bones become more and more visible as animals lose condition and correspondingly, fat and muscle.

Most cats, except for certain breeds, should be curvy and not angular. Impart your common sense into your body condition scoring. An obese cat that suddenly becomes ideal may be more of a cause for concern than one that has gone from ideal to underweight.

Weight loss is a nonspecific symptom in cats

Once you establish that your cat is losing weight, finding the cause is your next challenge. Like vomiting, weight loss in cats is not terribly specific.

Your veterinarian can help determine the possible reason for your cat’s weight loss based on your pet’s history, age, duration of the problem, other symptoms, and diagnostic tests.

Common Causes of Feline Weight Loss

By no means exhaustive, the following list includes many of the ailments that may cause a cat to inexplicably lose weight. A couple that we do not mention cause weight loss exclusively because your cat stops eating.

  • Dental disease – Pain and infection in the mouth or poorly occluded or broken teeth will prevent your cat from eating; A thorough oral exam will be a part of any veterinarian’s evaluation of feline weight loss
  • Pancreatitis – Signs are subtle in the cat but often include vomiting and dehydration.


Intestinal worms and other parasites are a leading cause for kittens to fail to gain weight and otherwise appear unthrifty. Roundworms are extremely common but easy to diagnose with microscopic examination of the feces for eggs.

Coccidia is a one-celled organism that can be resistant and cause persistent diarrhea as well as weight loss in small kittens. Also diagnosed by microscopic fecal examination, coccidiosis is much more difficult to detect than worms and often, treatment is presumptive.

Adult cats and kittens can suffer from tapeworm infestations most commonly secondary to fleas. Tapeworms do not often cause weight loss, but a chronic infestation is always something your vet will want to rule out. You can frequently achieve a diagnosis by visualizing tapeworm segments in the stool.

Fleas and ear mites are external parasites that can cause weight loss in cats. Some cats are sensitive to the pain and discomfort associated with flea bites so much so that they are distracted from eating. Others can suffer from allergies to flea saliva.


Hyperthyroidism, or the production of too much thyroid hormone, is a leading cause of weight loss in older cats. At first, the symptoms seem like good side effects with weight loss in a heavy cat and increased activity. However, the weight loss can progress to emaciation, and an overactive thyroid gland has detrimental effects on the heart.

Signs in addition to dramatic weight loss and cardiac disease can include a rapid heart rate, a heart murmur, hyperactivity, difficulty breathing, aggression, increased appetite, vomiting, diarrhea, and increased thirst and urination.

Veterinarians will diagnose hyperthyroidism based on a screening panel of the blood. If a baseline thyroid hormone level is high as well as the level of suspicion, your vet may send a thyroid panel to a special laboratory.

Organ Disease

The two major organs often associated with a cat’s sudden weight loss are the kidney and liver. Many times, the loss of body condition is only one of many symptoms.


Kidney decline is yet another leading cause for cats to lose weight. Many cats with renal insufficiency lose their appetites. However, cats with failing kidneys lose weight over time regardless if they continue to eat or not.

Kidney issues become more prevalent the older your cat gets. Cats between 10 and 15 years old have twice the probability of developing renal insufficiency as those up to the age of seven years, according to Hillpet.com.

Causes of renal insufficiency include compromised circulation to the kidneys, toxins, high blood pressure, and secondary effects of other diseases. A diagnosis is easy to confirm from the results of a blood chemistry panel.


A blood chemistry panel may detect liver disease, although an abdominal ultrasound and a tissue biopsy may also be useful.

Cats can experience a wide range of liver troubles and manifest symptoms such as vomiting, jaundice, lethargy, depression, inappetence, and loss of weight. Since the liver controls so many functions, its diseased state has far-reaching effects on blood clotting, the kidneys, and the skin.


Viral or bacterial infections can cause a rapid decline in weight for a cat. Severe and chronic viruses cause the wasting of muscles and fat.

Viruses that commonly affect more than just kittens and can cause weight loss are feline leukemia, feline AIDS, and feline infectious peritonitis. Cats get quite ill and often lose their appetites, but owners may realize after the fact that their pet had been gradually losing weight over weeks.

Upper respiratory infections are infamous for affecting the sense of smell in cats and thus making them inappetent. Diagnoses of viruses rely on history, symptoms, and testing that may include SNAP antigens kits or immune assays.

Bacterial infections show up through cultures if they become severe enough.


Chronic pain may cause cats to lose weight from inappetence or stress. Sometimes a complete physical exam will reveal a laceration or abscess that occurred months ago, explaining your cat’s mysterious weight loss.


Cancer commonly causes cats to lose muscle in a wasting process known as cachexia. Some cats also lose their appetites from tumor cells themselves, from the organ that cancer affects, or from the treatment. Diagnostic tools for cancer include examination, radiographs, ultrasound, bloodwork, biopsies, and advanced imaging such as CT and MRI.

Emotional Disturbances

Like people, cats can lose weight from stress. Frequently, they have a diminished appetite as well, but not always. Any big changes in your life will affect your cat.

Moving has a tremendous impact on an animal that does not appreciate change. Any new member like a baby or additional pet will require an adjustment from your cat. Your sensitive feline can experience distress and depression from emotional upheaval and may lose a significant amount of weight in a short time as a result.


In the diabetic cat, the body’s inability to handle blood sugar levels causes the cells to become starved of glucose, their fuel source. To make up for this shortage, the cat’s body will break down fat and protein in the form of muscles.

The initial signs of diabetes in cats are almost always weight loss, increased appetite, and an uptick in drinking and urination. You can probably see that the primary differential diagnosis is hyperthyroidism.

Diabetes in cats is similar to the disease process in humans in that it often involves insulin resistance. Type I diabetes, or the inability to produce insulin, is rare in cats.

Your veterinarian will diagnose diabetes based on your cat’s history, signalment (age, breed, body type), blood chemistry, and blood glucose levels. Since stress can temporarily elevate blood sugar levels, your vet will perform serial blood glucose levels if the results are in doubt.

Causes are not clear, but risk factors include obesity, repeated bouts of pancreatitis, breed, gender, and steroid use.

According to NCBI Resources, diabetes is more prevalent in the Tonkinese, Burmese, and Norwegian Forest Cat. The disease is also one that veterinarians see more often in male cats than females.


A cat that loses weight over several months could be experiencing food allergies or intolerance. Many of these cases are accompanied by other signs like intermittent vomiting and diarrhea. Allergies may also set up inflammatory bowel disease.

IBD can also rise as a separate disease, and cats may become anorexic or simply lose weight. Chronic or intermittent diarrhea commonly leads to weight loss.

When do you want your cat to lose a few pounds?

Overweight cats are at a greater risk of certain disorders similar to people. You can see an increased incidence of heart disease, Type II Diabetes, intra-abdominal tumors, and arthritis.

The sooner you can see that your cat is overweight and take steps to correct it, the more effective any weight loss programs will be. This is where performing your regular body scoring evaluations is key. You can utilize several methods in combination or one at a time to achieve weight reduction in your pet.

  • Exercise – Easy to neglect; Cats need daily exercises with mental activities included. Be imaginative to get your cat moving; Remember, cats have adapted to short bursts of energy expenditure as opposed to many dogs that worked for hours, so tailor your sessions accordingly
  • Make your cat work (tricks) or walk to food
  • Toy puzzles
  • Low carbohydrate diet – Read labels or ask your vet about effective prescription diets or special formulations
  • Hide meals – Accomplishes exercise and mental stimulation at the same time
  • Many cats can walk on a leash – Try to train yours; You can also try a treadmill
  • Indoor kitty condos – buy one or create one that your cat must use to get from one area of your house to another.
  • Find a compatible second cat

You should aim for your cat to lose about a half to a pound of body weight per month. Even morbidly overweight animals should approach their ideal weight within six months to a year.

Cats that lose weight too quickly or suddenly stop eating are at risk of a life-threatening disease called hepatic lipidosis or fatty liver syndrome. The liver accumulates an excessive amount of fat and becomes dysfunctional.

Treatment of fatty liver disease involves a feeding tube and rehydration. The prognosis is poor without early hospitalization. Hepatic lipidosis can also occur with any of the diseases that cause weight loss such as diabetes.

How do you know if your cat’s weight loss is serious?

You may be aware that your cat is losing weight, but when do you need to seek medical attention?

  • Any chronic weight loss that is unintentional
  • Sudden and unexplained weight loss
  • Drastic weight change that involves a percentage of your cat’s original weight in only a matter of weeks – Weight loss over days may indicate dehydration as well
  • You put your cat on a diet, but she loses weight that you notice within days instead of weeks
  • Weight loss accompanied by other symptoms such as a change in behavior, lethargy, or vomiting
  • Your cat moves from an ideal body score to underweight or thin
  • Any weight loss that makes you concerned

What are some solutions to weight loss in cats?

  • Appetite stimulants _ your veterinarian may prescribe appetite stimulants for cats with cancer or chronic illness.
  • Address underlying problem – Eliminate parasites, provide insulin and dietary modification for diabetics, or employ iodine radiation therapy for overactive thyroids
  • Exercise to build muscle mass
  • High protein diet – Cats evolved to obtain most of their energy from lean protein and a little fat.

Video Reinforcement


If you are trying to get the weight off your cat or keep an ideal feline healthy, this video shows examples of using your imagination.

It shows an elaborate kitty condo or obstacle course that satisfies a cat’s curiosity and love for high places. By catering to what cats enjoy, the obstacle course gets the cats engaged and active. Other ideas are lures, lasers, balls, and cardboard boxes.


This video provides an excellent synopsis of hyperthyroid cats. Many cats suffering from the disease are just like Ringo.

  • Older cat
  • Losing weight
  • unkempt – Not as careful groomers
  • Urinating excessively
  • Increased, voracious appetite

Note the emphasis on ruling out other causes of weight loss. Moreover, hyperthyroidism can occur concurrently with other hormonal disturbances like diabetes.