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Why Is My Cat Thin At The Back End

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Our feline companions come in all shapes and sizes, with long silky coats or no fur at all. Their one of a kind appearance is part of their allure, but there are certain changes that can be indicators of an underlying condition.

Even though everything about our kitties can be unique, weight loss or a shift in your kitty’s physical appearance like being thin at the back end might require more attention.

Why is my cat thin at the back end? While a cat’s rear end is usually slightly narrower, muscle water on the hind end can be caused by age, lack of eating, specific illnesses, or even depression. If you notice a change in the condition of your cat it’s important to consult your veterinarian. 

But let’s dive a little deeper into what could be causing thinness in the hind end starting with actually defining what “thin” means.

What Is Thin In Cat Terms?

I’m sure some of us have seen stray cats and were saddened by their scrawny appearance, and despite how cute chunky cats can be we also know the issues that heavy cats deal with. But do we know what an ideal cat looks like when it comes to size and weight?

Veterinarians commonly use a Body Condition Score (or BCS) to describe the weight and body condition of their patients. You can see veterinarian Christie Long discuss the basics of the BCS system in this video:

You can read more about the scoring system here but the basic description of a cat at an ideal body weight includes “visible ribs, no palpable fat, severe abdominal tuck, easily palpated lumbar vertebrae, obvious waist behind ribs.”

The ideal weight can be observed on a cat whose, “ribs are palpable, but with minimal fat covering. There should be a noticeable waist behind the ribs, a slight abdominal tuck with no fat pad.” And while the ideal cat is well-proportioned, the overweight cat has “more fat, there is no distention of the abdomen, no waist and there are extensive abdominal fat deposits, etc.”

This medial center has noted that muscle condition score is also important. “Muscle condition score is assessed by visualization and palpation of the spine, scapulae, skull, and wings of the ilia.”

What’s important to remember is that “Muscle loss is typically first noted in the epaxial muscles on each side of the spine, muscle loss at other sites can be more variable.”

How To Tell If Your Cat Is Thin At The Back End?

In some cats weight loss might be harder to notice. Some cats lose weight gradually, which might make it less evident, and if you have a long-haired cat, their weight loss might go unnoticed beneath all that fluffiness.

If you’re not able to understand whether your cat is too skinny visually, or you’re simply not sure, then use your hands. Feel your cat’s ribs, if they look or feel like the knuckles on your hand then they’re probably underweight.

The feeling should remind you of the feeling of the back of your hand, where you can’t really feel your bones, but you still can sense a hardness.

Run your hand down their belly if it’s sucked in then it means that they’re skinny. Visible backbone, very pronounced hips, and spine are all indicators of an underweight cat.

Looking at your cat from above might give you a better perspective, a smooth tucked-in waist is good, but built-up fat where the tail meets your cat’s back, or if your cat’s hips are sticking out then that’s a sign of an over or underweight fluffball.

Veterinarians use the Body Condition Score to assess a pet’s weight. You can find a body condition score chart online, or from organizations like the American Animal Hospital Association to determine if your cat is too skinny.

But self-diagnosing isn’t always advisable because weight loss could be a sign of something more serious. So, a visit to your local vet should be your first choice.

Why Is Your Cat Thin At The Back End?

Noticing your cat’s weight change can be alarming and it can become quite evident if you look at their rear. In those moments it’s important to ask ourselves, why is my cat thin at the back? Did something change in their day to day life?

1. It’s Part Of Their Breed’s Physique

Some cats can have different body structures, while they have the same weight some might look thinner others might look bulkier. Cats like Maine Coon and Norwegian Forest cats are sturdy animals, built to survive in harsh environments.

Their bulky size is part of their breed’s physique. If they were to become thin at the back end, the owner most probably wouldn’t notice just by looking at them. That’s why feeling your cat’s body is important in that case.

But then there are cats that you can clearly see that they’re thin, but it might be part of their breed’s description. Devon Rex for example is a breed of cats known for their slender bodies and skinny legs, not too different from the Sphynx except for the lack of fur in the latter.

The Peterbald and the oriental shorthair cat are also medium-sized and lithe, neither bony nor flabby cats.

Cornish Rex and the Russian blue are also two breeds with long slender bodies. They might be muscular but they’re fine-boned and might even have a fragile look to them, which could confuse you thinking that your kitty is thin at the back.

If you’re the owner of one of these breeds, especially if that’s your first time you might be surprised by your cat’s thin appearance. Of course, if you notice your kitty lose weight or if they look weak then it’s important to get your vet’s opinion.

Read Next: Cornish Rex Vs Devon Rex: Which One Will Be Your Choice?

2. Your Cat Is Getting Old

As with most creatures on this planet, with age comes change and muscle wasting is common in older cats. A healthy loss of weight will result in the loss of fat, but if a cat is sick or injured, they’ll mostly lose muscle, and in this case, it’s called cachexia.

This usually happens to cats that have common diseases like heart and kidney disease or cancer. However, with aging cats muscle loss is called sarcopenia. This means that even healthy senior cats have less muscle mass than younger cats.

Body Condition Score and Muscle Condition Score can help you assess the body fat and the muscle mass of your cat. It’s important knowledge to have especially if your cat is aging, and in case you notice your cat becoming thin.

Spotting muscle loss early on can help bring better results with the right treatment provided by your veterinarian.

3. Loss Of Appetite

The loss of appetite could affect both senior cats and young cats and there could be different reasons behind this problematic behavior. You might find your kitty rejecting food altogether or they might be eating here and there, a portion that will keep them from starving, but it will reduce their weight significantly.

They Don’t Like The Food

It took me a while to become educated on which brands are healthy for my cat and which are more like fast food. Through this personal growth my cats had to try a few cat foods before we finally settled on the one, they liked and the one they needed.

In this journey I saw my cats eat too much food and never feel full, I saw them reject certain brands completely and others they tolerated, but didn’t really like.

When my veterinarian told me that I need to be careful with one of my cats that could face kidney issues, we changed his diet and now he’s happier than ever, being healthy and eating tasty food.

Thinnes on the backend could be related to your cat just eating less. Perhaps your cat doesn’t like the specific flavor of the food or the overall taste. They might not like the texture as well, some cats might prefer dry food, others might prefer wet food in the form of pate, mouse, or with sauce.

If you’ve noticed their food bowl being full most of the time or if they keep throwing up the food you give them, it might be time to find the one food they might actually enjoy eating. But as always you might want to check in on your local veterinarian to rule out a more complicated concern than just being a picky eater.

Dental Discomfort Or Pain

Tooth and gum disease is also very common in cats, especially as they get older. Studies have shown that “between 50 and 90% of cats older than four years of age suffer from some form of dental disease, but fortunately, the most common forms of these diseases are largely preventable or treatable with appropriate preventative dental care and monitoring.”

According to this scientific journal, “cats with severe oral disease had a significantly lower soft and dry food intake when compared with those with minimal oral disease.” Of course, there are some cats that won’t stop eating, even though they’re in pain.

Maven Veterinary Care explains how dental problems can also increase the risk of heart, liver, and kidney disease. This is why it’s crucial to take your cat for a regular oral exam and teeth cleaning. Of course, brushing your cat’s teeth at home will also help prevent the spread of dental disease.

Difficulty To Digest

Your cat might have problems with digestion because of their food or a digestive disorder is the one causing them to lose their appetite. While having an upset stomach once in a while is normal for anyone, frequent diarrhea or vomiting could be a sign of a digestive disorder.

If you have a long-haired cat you might find them vomiting hairballs which could cause problems with the digestive tract or vise versa.

According to Dr. Jane Brunt, CATalyst Council’s executive director, and feline veterinarian, “what’s important for owners to know is that hairballs are not normal.” It seems that hairballs might be caused by a problem with the gastrointestinal tract.

Dr. Brunt also explains why hairballs should be a common occurrence by stating that, “the cat has developed a digestive tract that, when it is healthy and working correctly can handle normal amounts of fur without a problem. Even long-haired cats should not develop more than one or two hairballs a year.”

4.Underlying Condition Or Illness

While you might be looking for a simple explanation it’s important to look into the answers we might not like. Losing weight can be the result of a certain health condition, and it’s important to look for more signs in order to help our kitty become healthy again.

Diabetes Mellitus

With this condition, a cat’s body isn’t capable of producing or respond properly to the hormone insulin. With diabetes, the levels of sugar glucose, which is the main source of energy for the body, are high. According to research, “0.2 and 1 percent of cats in the general population are believed to suffer from diabetes.”

Margarethe Hoenig, a Professor of the Department of Veterinary Clinical Medicine, has found that “Obesity, together with age and gender, is one of the most important risk factors in cats.” She also states that “owner education about controlling caloric intake is the most important aspect of lowering the risk of diabetes in cats.”

Weight loss is an important sign, so if you notice your cat becoming thin at the back end it could be because the cells in their body can’t absorb glucose from the blood. This loss of glucose means that your cat won’t get the energy it needs. You might notice your cat’s appetite increasing, but their body fat will be decreasing instead.

If you notice a loss of muscle mass in your cat while their appetite is still the same or increased you should visit your veterinarian.

Increased thirst and urination can also be signs that your cat has diabetes, but also other diseases. Your vet will run tests on your cat’s glucose concentration in the blood and urine to determine if diabetes is the disease affecting them.


A disease like hyperthyroidism is quite common in cats and it’s mostly observed in middle-aged and older cats. An increase in the production of thyroid hormone from an enlarged thyroid gland in a cat’s neck results in hyperthyroidism. Usually, this enlargement is caused by a non-cancerous tumor, but it could also be caused by malignant tumors.

When it comes to hyperthyroidism, you should look for signs like weight loss, increased appetite, thirst, and urination. You might also expect to find your cat vomiting, having diarrhea, being hyperactive and you may find your cat’s coat looking matted or greasy.

If you have an older cat, you definitely should be on the lookout for these signs.

In order to fully diagnose hyperthyroidism, your veterinarian will need to submit bloodwork and check your cat’s thyroid levels.


While feline obesity is usually linked with cancer in cats, weight loss could also be an indicator. Anemia could also be associated with weight loss in conditions like cancer. Since cats can be prone to specific types of cancer, like soft tissue sarcoma, squamous cell carcinoma, lymphoma, and a type of blood cancer, make sure to get your vet’s opinion on the matter.


If you took in a stray cat from the street, it’s important to run a few tests to make sure your new companion is healthy. There are many dangerous things besides cars and parasites out there for cats and one of them is feline immunodeficiency virus (FIV). While similar to HIV, this virus only infects felines.

FIV attacks the cat’s immune system, which as with humans, makes them more vulnerable when it comes to other infections. Cat’s infected by this virus might not show any symptoms for years until they catch a severe illness.

Recent studies have found that cats infected with FIV can live normal life spans unless they get infected with the feline leukemia virus. Infected cats can have a loss of appetite, diarrhea, and other problems which can lead to progressive weight loss.

Gastrointestinal Tract Digestive Disease

According to Dr. Sina Marsilio, a Veterinarian in the Gastrointestinal Laboratory at the Texas A&M College of Veterinary Medicine & Biomedical Sciences, “the most common clinical signs of digestive disorders in cats are loss of appetite, lethargy, vomiting, and diarrhea.

It’s also important to note that weight loss in senior cats, is a common sign of gastrointestinal disease. Problems with chewing or swallowing which can have something to do with the cat’s teeth or esophagus are also signs, Marsilio states.

If your cat has access to the outdoors, they might have eaten something harmful, or something that they’re allergic to. Dairy products and even toxic plants can result in diarrhea and loss of appetite.

There are also parasites like Giardia, roundworms, tapeworms, and other bacteria that can affect your cat’s digestive system. Even if your cat is a strictly indoor companion, they might still contract one of these parasites from our outdoor shoes. That’s why regular vet check-ups are important as well as frequent antiparasitic medication.

5. Stress, Anxiety, Or Depression

Cats can get stressed out from minor changes and most of the time it has to do with the simple fact that they’re creatures of habit. If there were some recent changes to your cat’s environment lately, then don’t be surprised if you find them eating less and as a result, getting much thinner.

A change in their feeding routine or the brand of their food could cause stress. A dirty litter box could also add to their discomfort. If your kitty is the type to enjoy their alone moments, having people over or moving home to an environment where there’s too much noise could possibly have a negative impact on their wellbeing.

If you’ve had someone new living in your house, or you’ve brought another pet to keep your cat company while you’re at work, that’s enough to make your kitty anxious and even depressed.

On the other hand, if you had two cats that were bonded and one of them passed away, this could also be a reason for your cat to become depressed. The symptoms are usually loss of appetite, a lethargic state. According to some studies, even healthy cats could act sick when changes happen in their environment.

Finally, a senior cat could also develop cognitive dysfunction, also known as dementia. According to ASPCA, “cognitive decline – referred to as feline cognitive dysfunction, or FCD – affects more than 55% of cats aged 11 to 15 years and more than 80% of cats aged 16 to 20 years.

Your senior cat might become disoriented, stop eating, and lose weight as a result. If you notice drastic changes in your cat’s personality, a vet, or a cat behavioralist could help you deal with your kitty in a way that will benefit both of you.

What To Do If Your Cat Is Thin At The Back End?

As cat owners, we should try and be observant of our loving furballs. Even though cats can be quite good at hiding their pain, we still have to see through them and look for small clues that indicate pain or discomfort. You might find your cat purring all the time, but this might actually be a clue that your kitty is in pain since it promotes healing.

If you notice your cat becoming thin at the rear, then there are a few things you could do to make sure your feline companion is healthy!

Visit The Veterinarian

Any alarming changes in your cat’s appearance and behavior should first be checked by your vet. Even a question that might seem innocent like, why is my cat thin at the back end, should be treated seriously. If you’re not sure, you could call your vet and explain to them the situation.

A good veterinarian will ask you some important and detailed questions about your cat’s general wellbeing. But because cats can show signs of a more serious condition way too late, seeing them only lose some weight should be enough to visit your local pet clinic.

Your vet should perform a thorough physical examination. Depending on your kitty’s condition they’ll do some blood and laboratory tests. In case your kitty needs treatment you should listen to your vet and follow their instructions. If you’re not completely sure, you could ask for a second opinion from a different veterinarian.

Neglecting yearly check-ups, vaccination, and antiparasitic medication can be harmful to your kitty’s health. The older they get, these visits might have to become even more frequent.

Give Your Cat High-Protein And Nutrient-Rich Food

If your visit to the vet shows you that your cat is completely healthy then you might want to look into your cat’s diet. Whether your cat is super active or they’re a bit on the lazy side, nutritious food with lots of protein is necessary to help your skinny cat gain their healthy weight again.

Wet food might also prove more beneficial since it’s high in protein, which should help maintain your cat’s muscle mass. In the journal of the American Veterinary Medical Association, Debra L. Zoran, DVM, Ph.D., DACVIM, states that “cats are metabolically adapted to preferentially use protein and fat as energy sources”.

Foods with high protein, help maintain your cat’s lean body mass (LBM), as shown in some studies. Muscles, bones, ligaments, organs are part of the LBM and they are the main source of metabolic activity. This activity supports vital actions like mobility, immunity, and more.

Your vet might also recommend a specific diet for your cat, especially if they have a certain condition or if they’re a senior cat. Perhaps you could look into specific cat food brands that don’t use fillers and have more protein. You could also consult with your vet if your kitty is in need of high-calorie supplements.

Make Their Food Tastier

There are cats that can be quite picky when it comes to food and they prefer certain tastes. My cats can’t stand dry food that has fish as their main component, and they go crazy from chicken. Strangely enough, when it comes to wet food, it’s the other way around.

Canned food in the form of pate or mouse, is also a big no for them, but when there’s sauce, then they can’t get enough of it!

Perhaps you could enhance the flavor of your kitty’s food by adding some tuna water into the mix. Cook some fresh chicken or beef and use small portions as treats as well. During the summer you can keep the food cold in the fridge which your kitty might find refreshing as well as tasty.

Experiment with texture, flavor, and consistency. Perhaps your kitty prefers small portions a couple of times a day instead of one. Since wet food tends to dry out quickly this method might help your kitty enjoy fresh portions all day.

For cat parents that are away for half the day, it might seem like an impossible task. That’s when an automatic wet food feeder comes into play.

Keep Your Pet Hydrated

Make sure that your kitty has always plenty of water nearby so they can drink it at any given time. I’d suggest you keep their water bowl away from their food because they might be reluctant to drink it. You see cat’s in the wilderness wouldn’t eat next to a water source to avoid contamination.

Water is the main source of a cat’s hydration. Wet food can also help your cat stay hydrated, unlike dry food. But apart from food and water, there are a few more things you could add to your cat’s hydration routine.

A bone broth could keep your kitty hydrated while also adding beneficial nutrients to their diet. This doesn’t mean that they won’t need regular water of course. On warm summer days, you could freeze the bone broth into cubes and give it as a refreshing treat to your cat.

Finally, a bit of tuna water as mentioned before could also help them enjoy their food more if it’s mixed in or even in their water. Of course, it’s not something that you should go overboard with, but see it instead as a treat to make your kitty happy and extra hydrated. Avoid tuna that’s kept in oil and watch out for the salt content and you’ll be good to go!

Closing Thoughts

When it comes to cat care there are so many questions, we might find ourselves asking. Why is my cat thin at the back end, might actually be one of them! And this is good because that means you’re an observant and caring cat parent.

The next step would be to take your kitty to the vet and tend to all their needs in order to solve this mystery. And if you’ve reached this section all the way from the very top, then I’m sure that’s just what you’ll do.

Now tell us, have you ever asked yourself or your vet, why is my cat thin at the back end? If so, what did your vet told you and what did you do to make your cat’s booty pop again?