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Weight Loss in Cats: Causes & What to Do

Weight Loss in Cats: Causes & What to Do
by KatKin Team

Read time: 3 min

When it comes to cat weight concerns, most of the conversation focuses on them being too fat. Around 60% of cats are overweight or obese. So it makes sense that this is the topic on everyone’s minds. But your cat can be underweight too. And it can be a problem.

Worried that your cat doesn’t have enough meat on their bones? Read on. 

Why is my cat losing weight?

Sudden or mysterious weight loss can be worrying. Even if your cat is technically overweight, an unexplained drop or change might be because of something sinister.

Make sure you make yourself familiar with your cat's normal weight. Have them weighed regularly and use our Body Condition Score chart. So you can keep a close eye on any changes in your cat’s weight. 

If you notice any dramatic, sudden changes in your cat’s weight, it might be time to take them to the vet. If they lose  a lot of weight, particularly if you’re not trying to help them slim down, it could be a sign that they’re unwell or in pain. 

Cats are very good at hiding any pain or discomfort. Which makes it really hard to tell when they’re ill. So if you’re noticing sudden weight loss, it’s time to pack them off to the vet to make sure they’re not sick or in pain. 

Weight loss in cats: causes

Sudden weight loss might be caused by:

  • Stress or anxiety

  • Worms

  • Diabetes

  • FIV (Feline Immunodeficiency Virus)

  • Hyperthyroidism

  • Cancer

  • Organ failure

  • Dental disease

  • Arthritis or loss of muscle mass

Not getting enough food

One of the biggest, and least harmful, causes of sudden weight loss can be the most obvious: simply not getting enough food. If you spot your cat getting skinnier and there’s no sign of any sickness or pain, take a look at their food bowl. They might be eating less than you think. 

Do you have other pets? Another cat or dog might be finishing their dinner for them. Or chasing them away from their bowl. You may want to think about feeding your cat in another room, away from other pets to make sure they can eat their fill and put weight back on. 

Other pets not a problem? Check out the back of their food packet. If you’ve recently changed food brands, there might be fewer calories. And your cat might not be getting what they need to maintain their weight. 

Make sure your cat’s food bowl is in an easily accessible spot. If your cat is getting on a bit in age, they might be less willing to jump onto a counter or high surface for their meal. Make sure it’s placed lower down so they can reach it easily. 

If your cat is allergic to certain ingredients, they might not be absorbing the correct amount of calories. Itchy skin, thinning fur, upset stomach and vomiting after eating might mean they’re allergic to something in their food. Try switching them to a sensitive stomach cat food. Or KatKin – our fresh food doesn’t contain any of the common ingredients and fillers that cause allergies. 

How to make a skinny cat gain weight

If you think your cat is a bit too skinny, take them to the vet before doing anything else. If your vet thinks they just need to eat more, you can start upping their calorie intake. 

  • Healthy (but skinny) cats may simply need more calories a day. This could look like an extra meal. Or a midnight snack. KatKin is formulated with your cat’s ideal weight in mind. So if you already feed them our delicious recipes, they’re already getting all the calories they need. 

  • If you have multiple cats, one might be stopping the other from eating. Separate your skinny cat from the greedy one at dinner time. Pop them in another room and allow them to eat their meal in peace. Make sure you remove extra food when they’re both done to avoid fighting.

  • Nervous or anxious cats will be more willing to chow down in a calm, quiet space. Away from noise, appliances, children, and other pets. 

  • If you feed your cat dry kibble, offer them something extra tasty as well. Canned food, KatKin fresh cat food, or toppers like cooked, shredded chicken or flakes of tuna.

  • Picky cats might be encouraged to eat more if they’re offered a variety of flavours and textures. Here at KatKin, we offer a wide range of delicious recipes in 2 different textures: smooth and chunky.

  • Make their food extra tempting by popping it in the microwave for a few seconds. (Not too long. So they don’t burn their mouths.) When their food is warmed up, it smells much more appetising. We’d all rather eat a hot roast dinner rather than one that’s gone cold, wouldn’t we?

  • Try adding a small amount of  tuna juice (fresh water, not oil or brine) to their dinner. Or a spoonful of unsalted chicken broth. Or even a dusting of our Sprinkles to entice them to the bowl. 


You’ll probably notice that your cat will start to lose weight as they get older. Senior cats can’t absorb fat and protein as well as they could when they were younger. They can lose around a third of their lean body mass this way. (That’s the weight your cat would be without any fat on them.) This is fairly normal, and just means they need a higher level of nutrition to maintain their body weight. 

Do cats lose weight as they age?

It's normal to see some weight loss. But if your elderly cat has suddenly lost a lot of weight, it’s time to take them to the vet. There are a number of health conditions that can cause a sudden drop in body weight. So it’s best to get them checked over. 

Older cat losing weight but still eating

If your OAC (old-age cat) is losing weight even though they’re still eating, they could have some kind of underlying health condition. One of the most common conditions older cats are susceptible to is hyperthyroidism. This is a condition in which the thyroid works overtime and can cause your cat to lose weight even with an increased appetite. They may also be more thirsty and urinate more. And their fur could become a bit greasy-looking. 

If you’re worried about your elderly cat for any reason, take them to the vet. 

What to feed an older cat that’s losing weight

Making sure your older cat is getting a better level of nutrition is essential to help them maintain their weight. If you haven’t already, and they’re over 7, it’s time to switch them to a senior cat diet. Or switch to KatKin’s fresh cat food. We formulate every meal to your cat’s needs. Taking their ideal weight, current weight, age and body condition into account. 


Cats hate being stressed. Unfortunately they can get stressed pretty easily. Lots of stress can cause your cat to go off their food, leading to weight loss if they go long enough without eating enough. 

Try to identify the cause of their stress. Children, new pets, moving house and construction work are all common stressors. You can’t do much about moving house. But try to remove the other stressors as best you can. Or remove the cat from the situation. Feed them in a quiet, private space to keep them calm. You may want to consider using a calming plug-in device temporarily too. 


Being unwell puts most of us off our food. So it’s common for cats to lose weight when they’re sick. But some illnesses might actually make them feel more hungry while they still lose weight. Which is worrying. Here’s a list of potential illnesses that can make your cat lose weight. 

  • Diabetes. This condition prevents your cat’s cells from absorbing enough glucose from their blood, which is how the body gets energy. They might be more hungry and thirsty than usual but not able to put weight on if they have diabetes. 

  • Parasites. If your cat has worms, this can cause them to lose weight as the parasites will be absorbing the nutrients instead of your cat. They might be extra hungry, feel bloated in their tummy and have an upset stomach. You might even see worms or their eggs in their poop. 

  • Organ failure. Most common in elderly cats, organ failure can make your cat lose a lot of weight. This is diagnosed by blood test.

  • Dental problems. If your cat’s mouth hurts, they’ll be less likely to eat. We don’t blame them. Make sure you’re brushing your cat’s teeth regularly. If they’re drooling, hissing when they eat, or rubbing their face a lot, it could be because they’re in pain. 

  • FIV. Feline Immunodeficiency Virus is similar to Human Immunodeficiency Virus (HIV). It basically means that your cat’s immune system doesn’t work as well as it should. They might get frequent minor infections, have enlarged lymph nodes, and you might see inflamed gums on them as well. The good news? It’s very treatable and they can live long happy lives with good management.

  • Hyperthyroidism. As we’ve mentioned before, if your cat’s thyroid is working in overdrive, this can cause them to lose weight rapidly. This little organ in the throat is responsible for managing metabolism and when it is overactive, the body metabolises food too fast to absorb the right nutrients. 

Cat losing hair and weight

If you spot that your cat is losing hair and weight, there are a number of things that could be causing it. 

Things like stress and anxiety, certain types of cancer, pregnancy or nursing, hyperthyroidism, gastrointestinal problems and bacterial or fungal infections are all culprits for their thinning fur. Parasites and ringworm can also be a cause. 

If your cat looks a bit more patchy than they were and is losing weight at the same time, take them to the vet.

Cat losing weight in hindquarters

You might notice that your cat is losing weight in the hindquarters. They’re usually slimmer and more muscular in this area. Which makes any weight loss here much more shocking. Weight loss can make their hips look sunken in, with the base of the spin sticking out more than normal. This is commonly due to a loss of muscle mass. And it’s a sign that something is wrong. So make sure you take them to the vet.

Cat losing weight but eating and acting normal

Cats are really good at hiding when they feel unwell. So if your cat seems to be eating normally but is still losing weight, it doesn’t mean they are fully healthy. Conditions like diabetes or hyperthyroidism might mean your cat still eats plenty and even has an increased appetite. But they can be life threatening. So it’s important to take them to the vet if you notice any rapid or unplanned weight loss. 

Discuss cat weight loss with your vet

If you’re worried about your cat’s weight at all, it’s a good idea to call your vet. It could be simple and they just need more food. But it could be something that needs medical help. Better safe than sorry. 

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