Obesity in Cats and its Health Impact

Obesity is a growing epidemic among the cat and dog population and has become the most common nutritional disorder seen in cats. Up to 45% of cats who were examined by a veterinary professional were found to be obese. That is a staggering number and frighteningly it the situation is getting worse.

Key points

  • A cat is considered to be overweight if his weight is 15% above his or her optimal weight, and is obese if above 30% optimal weight.
  • It is most common in middle-aged to senior cats.
  • Causes include dietary, inactivity, certain medications and underlying medical disorders.
  • Obesity can severely impact a cat’s quality of life, and several health concerns can develop as a result of obesity which includes diabetes, kidney disease, arthritis and cancer.

It’s easy to ignore obesity because, for the most part, an obese cat doesn’t look or act sick, but this is a slow and insidious problem that over time has a detrimental to his overall health and quality of life.

People often show love for food, and pet owners can experience guilt if they try to restrict food intake, but we are quite literally killing our cats with kindness.

When cats gain weight, the fat accumulates beneath the skin (subcutaneous fat) which is what most people think of, but there is another type of fat that can be found within the abdominal cavity, surrounding the organs such as the kidneys, pancreas, and liver. This is known as visceral or intra-thoracic fat. What is known in humans is that it is the major culprit in many health problems associated with obesity. This type of fat is active, and it is now believed to be an important endocrine organ. It releases pro-inflammatory chemicals and hormones which lead to inflammation, insulin resistance, and even hunger. That’s right; visceral fat can make you feel hungry.

Some cats have a small paunch towards the back of their belly and just in front of their hind legs.

Sphynx cat with a visible primordial pouch


The most significant factors associated with obesity in cats is overfeeding (particularly free-feeding and high carbohydrate diets) and not enough energy expenditure (calories in vs calories out). If the calories consumed exceed calories burned, then the cat will put on weight.


Dry food has been the holy grail of food for two decades now. There is some movement away from this belief, but dry food is still hugely popular. I am not saying we shouldn’t feed any dry food, but is it as good for our cats as has been touted by pet food manufacturers and several veterinarians?

1) High carbohydrate food. The cat by nature requires a high protein diet, and most dry foods are high in plant carbohydrates. Cats synthesise protein and fat to use as energy; carbohydrates are converted to fat. Have a look at the ingredients list on dry cat food, they are always listed in order of weight, with the first ingredient being the most abundant one. On dry food, this is often cereal-based which is cheap compared to meat.

Cats in the wild ingest a tiny amount of grains and vegetables by eating the stomach contents of their prey, but the bulk of their food comes in the form of protein. More information on reading cat food labels can be found here.

2) Dry diets are very calorie-dense, with only 10% water content. Not only are cats getting excess calories, but they are not getting enough water (which is also filling). A cat’s natural diet of small rodents or birds consists of 70% water. Chronic dehydration can also have serious health on their urinary tract health because many cats don’t compensate for this lack of water in their diet by drinking more.

3) Dry diets are generally left out for cats to free feed and while most cats won’t scoff down their food in the same fashion as many dogs do, not all cats will self-moderate. It is very convenient for cat owners to put a scoop of dry food in the bowl and forget about it until it is empty.

4) Carbohydrates aren’t as filling as protein; therefore it is much easier for cats to overeat.

I also have to wonder if a part of this is down to human behaviour. Often people equate food to love and care. Are we quite literally over-loving our cats to death by our reluctance to say no? It may be as simple as giving them more food at mealtimes to make them happy, giving in to their cries for more food or sharing our snacks with our feline companions.


This may be a controversial one, but so many pet owners are keeping their cats indoors now for their safety (and rightly so). However, most pet owners don’t compensate for this by ensuring indoor cats remain active, with daily play sessions.


Certain medications can lead to weight gain in cats. Glucocorticoids are the most common type of drugs and can induce excessive hunger (known as polyphagia) in cats.


The thyroid gland is located in the neck and is responsible for producing thyroid hormone which regulates metabolism. Hypothyroidism is a rare disease in cats that is caused by an underactive thyroid gland.

Cushing’s syndrome

Cushing’s syndrome (hyperadrenocorticism) is an endocrine disorder caused by high levels of cortisol in the body either due to a tumour or medical administration. It is a rare disease in cats, typically affecting middle-aged to senior cats.

Excessive cortisol levels cause weight gain due to an increased appetite.


As the cat moves into his senior years his metabolic rate slows down, joints may become more painful, and the senior cat will be less active. A slowed down metabolic rate, and a decrease in activity can both lead to obesity in cats if we don’t modify their diet.


Some cats are more prone to weight gain than others. This is more common in certain dog breeds (such as Cocker Spaniels and Labradors for example) than in cats, but it still exists. Domestic shorthairs are the most commonly represented group.


We don’t want anybody to avoid desexing their cat for fear of weight gain. The importance of spaying and neutering all non-breeding cats cannot be overemphasised. Cats who have been desexed are slightly more prone to weight gain than entire cats due to a lower basal metabolic rate (along with decreased activity and increased food intake). However, this can easily be corrected by simply adjusting their diet accordingly just as we should with aging cats. It should be remembered that while desexed cats may be more prone to weight gain, there are several health risks associated with not desexing such as testicular and mammary cancer.

Health consequences

  • Diabetes – Insulin is a hormone produced by the pancreas, which is needed to transport glucose (from food) into the cells (I always think of insulin as a key to unlock a door to the cell allowing glucose to enter). Glucose is needed by the cells for energy, growth, and repair. Obesity leads to insulin resistance, which means glucose levels build up in the blood, but is not able to enter the cells, meaning they are unable to function as they should.
  • Arthritis – This painful disorder of the joints where cartilage (the smooth coating at the ends of the joints which helps them glide over one another) wears down. Excess weight places undue strain on the joints which over time causes the smooth coating to wear away.
  • Hepatic lipidosis (fatty liver disease) – This is a painful and life-threatening condition which develops when a cat stops or dramatically reduces its food intake. To make up for the shortfall, the body uses up stored fat, sending it to the liver to be processed. As the liver is not very good at processing fat, it quickly becomes overwhelmed affecting its ability to function properly.
  • Exercise intolerance – The larger your cat becomes, the harder it is for him to exercise which then becomes a vicious cycle, as he exercises less, he is likely to put on, even more, weight.
  • Skin problems – Obese cats are more prone to developing skin problems; a large cat may find it difficult to groom himself as effectively as a lighter cat.
  • Higher risk during anesthesia and surgery.
  • Heart disease due to excessive weight placing extra strain on the heart.

Other less talked about health risks associated with obesity such as the bladder, mammary and transitional cell carcinoma, reproductive disorders and urinary tract disease. Risk factors in obese dogs include a greater risk of heatstroke, cardiorespiratory disease, decreased immune function and high blood pressure.

Certain medical tests such as abdominal palpitation and ultrasounds are more difficult in obese cats.

The good news is that if a cat is allowed to lose this weight, its health risks can either be significantly reduced or in some cases completely reversed.


It is always best to ask your veterinarian if he/she believes your cat is obese. Cats come in all shapes and sizes, and therefore it is difficult to determine a standard weight that covers all cats and their differences. Veterinarians prefer to go by body condition and not a number on the scales.

To determine if your cat is overweight or underweight, the following guide can help.

  • Feel along the side of the cat. You should be able to feel the ribs, with a slight layer of fat covering them.
  • Stand above the cat, you should be able to see a waist, and have an hourglass figure.
  • There is a noticeable bulge on either side of the tail head.

Body condition score in cats

Diagnostic workup:

Your veterinarian will perform a physical examination of your cat. He/she will also want to perform some blood tests to rule out a medical cause of obesity such as an underactive thyroid (hypothyroid) as well as evaluate your cat’s overall health with standard tests including biochemical profile, complete blood count, and urinalysis


Veterinarians are there to help your cat and you. If you are unsure that your cat is overweight, book an appointment with your veterinarian. They can guide and help you all the way.

Weight loss requires close veterinary supervision as sudden and rapid weight loss can lead to hepatic lipidosis, which is life-threatening. Therefore NEVER attempt a weight reduction diet on your own. A safe guide is 1 to 1.5% weight loss per week. You and your veterinarian will work closely to ensure weight loss is achieved safely. Regular check-ins will be necessary.

  • Increase exercise: There are plenty of interactive toys on the market which will encourage your cat to exercise. Aim for 20-30 minutes of exercise a day, this can be split into two or three sessions. There are many types of cat toys on the market, buy a variety and try them all out on your cat. Some love to play fetch, others love to stalk and attack a wand toy. A favourite of my cats was Da Bird. I would recommend starting with shorter exercise sessions but more frequently initially. Jackson Galaxy recommends working with your cat’s hunt, kill, eat drive. A cat in the wild would stalk his prey, once caught he would kill and then eat it. Make your cat earn his dinner by mimicking what he would do in the wild. Allow him to stalk his prey (again, a wand toy is great for this), don’t let him catch it immediately, but make him work for it. After his play session, feed him (if it’s dinner time). This has so many benefits.
  • Take your cat for a walk: Another option is to train your cat to walk on a harness so he can get outside and explore the world while getting some exercise. Some cats take to a harness well, other cats will have nothing to do with it. Follow your cat’s lead (pardon the pun), and don’t force the issue if he clearly hates it.
  • Decrease caloric intake: There are prescription diets on the market specifically for cats, your veterinarian will be able to recommend the right diet for your cat. Switch to canned or raw diets. Cats can be extremely fussy when it comes to changes in their diet and if that happens, they can develop potentially life-threatening hepatic lipidosis.
  • Give him food he has to work for: Food puzzles, chicken wings or necks, cheap cuts of beef all slow down eating.
  • Water only: Once weaned, cats have no nutritional requirement for milk. Overweight cats, in particular, should be provided with fresh, clean water, milk contains unnecessary calories.
  • No treats: It’s easy to slip the odd treat to your cat, but this needs to be stopped completely.
  • Consider getting your cat a feline companion. Two cats are more likely to play than a cat on their own.
  • Feed 3-4 smaller meals per day instead of filling the bowl and leaving it down for your cat to graze on.

If the cause is medical and not diet-related, treating the condition should hopefully resolve obesity.

Have one person in charge of feeding your cat, it’s too easy for cats to double up on meals otherwise.

Once your cat has reached his target weight, maintain this by feeding a balanced diet that meets but does not exceed his calorific requirements. Remember, the older and less active the cat, the fewer calories he requires. As a general rule of thumb, I like to remove uneaten food after 20-30 minutes.


The prognosis is very good. Diabetic remission has been achieved in many cases once they go down to a healthy weight, he greatly reduces his chances of developing hepatic lipidosis and skin problems should resolve.

Unfortunately, arthritis cannot be reversed, however, there is less pressure on the joints in lighter cats, therefore slowing down the progression of the condition.


  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio

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