5 Common Causes of Weight Gain in Cats

Fact checked by  Jackie Brown
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Cats come in all different shapes and sizes, which means giving a standard ideal weight for a cat is difficult. However, each cat will have their own healthy weight, and pet owners should try their best to maintain a good body condition for their cats. Excess weight and obesity are a growing problem in pet cats and are linked to many health conditions such as diabetes and heart disease1.

Key Takeaways

Excess weight can impact a cat’s health and well-being, so pet owners should take steps to maintain a healthy body condition for their cats.

Common causes of weight gain include excess food intake, lack of exercise, age, and spay/neuter status.

Occasionally, an underlying medical problem might be to blame for weight gain in cats.

It is rare for feline obesity to be caused by a medical condition, and the causes of weight gain are usually centered around overfeeding and a lack of physical activity. Let’s delve into the details of weight gain in cats, and what you can do as a pet parent.

What Is an Ideal Cat’s Weight?

Your cat is likely overweight if you can’t easily feel your cat’s ribs with your hands.

Body weight in cats varies with breed, sex, age, and size. Each cat will have a different ideal weight, and this is best judged by assessing their body condition. Check your cat’s body condition regularly, perhaps as part of a grooming or dental hygiene routine, so even small amounts of extra weight or weight loss can be picked up on quickly.

Assess a cat’s body condition through gentle touch, as the fur can make visual assessment inaccurate. You should be able to easily feel your cat’s ribs along their sides with your hands, but the ribs should not be visible. Your cat should have a “tummy tuck” (an obvious waistline), with only small amounts of fat around the tummy. Overweight cats might have fat deposits around their lower back and abdomen, a lack of a waist, and the ribs will be concealed by excess weight.

The World Small Animal Veterinary Association (WSAVA) has published a useful guide for body condition scoring in cats. Once you understand how to assess your cat’s condition, it can be helpful to weigh them to keep track of the numbers.

If you don’t have a small scale to weigh your cat, the following method is useful for weighing a cat at home:

  • A household member first weighs themself.
  • This person then weighs themself again while holding the cat.
  • Subtract the person’s weight from the combined weight, leaving the cat’s weight.

Small changes to a cat’s weight can be significant, due to their small size, so accurate scales are needed.

Also Read: Cat Obesity Chart: Find Out if Your Cat is Obese

Causes of Weight Gain in Cats

Weight gain can be caused by medical or behavioral factors, or sometimes both.

If you’ve done a body condition assessment on your cat, and think they might be overweight, or have seen the numbers of the scales creeping up and are trying to avoid an obese cat, it is essential to determine why your cat is gaining weight. Knowing the “why” is needed to counter the problem. Read on for the most common causes of weight gain.

1. Inappropriate Food Intake

Some cats will overeat if free fed; serving measured meals can combat this.

Your cat’s diet is important in so many ways, but its mainstay is to provide the nutrition and energy that your cat requires for their daily life. When choosing a pet food, it is important to remember a few things.

A cat’s nutritional requirements will vary according to age and activity level, so it is important to choose a diet that is balanced, complete, and designed for their life stage. It is also worth noting that cats are carnivores, meaning that they require a diet high in protein but low in carbohydrates.

Cat food varies in its nutritional content, with some diets higher in fat and carbohydrates than others. A diet that is suitable for a kitten might lead to weight gain if fed to an adult cat, for example, as kittens require energy-dense food which is high in fats and calories.

It is also necessary to feed the correct amount of food that your cat needs. Overeating is a prime cause of obesity in cats2. You can choose to feed a wet food or dry kibble, or a mixture as long as the amount given is correct.

The food packaging should give you a guideline for how much to feed your cat, but remember that these amounts might need to be adjusted for your individual cat if they are gaining or losing weight on the suggested amount. Some owners chose “free feeding,” where cat food (usually dry food) is left out for the cat to eat ad-lib. Some cats will self-regulate well, but others will just eat and eat and eat if given the chance, so this method is not be suitable for all cats.

Also Read: The 7 Best Cat Foods For Overweight Cats

2. Physical Inactivity

Cats that don’t get enough exercise are at risk for becoming overweight or obese.

Cats are designed to be active, with athletic, graceful bodies and a predatory and territorial lifestyle. Modern domestic cats have less need for activity, with their food provided for them helpfully in a bowl, and smaller territories than their wild ancestors.

A lack of exercise correlates with a lack of calories burnt, making excess weight gain more likely. Indoor cats and senior cats are particularly prone to sedentary lifestyles, and their food intake should be adapted accordingly2.

Also Read: Why Do Cats Need Exercise and the 5 Things To Consider

3. Age

As cats age, they often continue to eat the same amount of food despite needing fewer daily calories.

Older cats tend to be less active, have a lower dietary calorie requirement than adult cats, and often sleep more than their younger counterparts. They might also have certain health conditions which affect activity levels, such as arthritis. Senior cats are particularly prone to obesity for all of these reasons.

Also Read: Why Is My Cat Not Eating? Loss of Appetite in Cats Explained

4. Spay/Neuter Status

A cat’s metabolism slows after spaying or neutering, but weight gain can be avoid with proper diet and exercise.

Once a cat is neutered, their metabolism alters, leading to a reduced calorie requirement2. Spayed and neutered cats are therefore more likely to become overweight than intact cats. Spaying and neutering cats is still recommended for many reasons, and this cause of weight gain can be avoided by alterations to their diet after the procedure.

Also Read: How Much Does It Cost to Spay or Neuter a Cat?

5. Health Conditions

Some cats gain weight due to painful conditions that make it difficult for them to be active.

A handful of health issues actively cause weight gain in cats. Some examples include:

  • Hypothyroidism (an underactive thyroid gland) is incredibly rare in cats, unlike dogs.
  • Acromegaly, a disease that involves increased production of growth hormones, can result in insulin resistance, diabetes, and weight gain.
  • Diseases that cause fluid retention, such as heart disease or feline infectious peritonitis (FIP) can cause a swollen tummy.
  • Some medications such as corticosteroids can lead to an increased appetite and weight gain.
  • Some health problems, such as arthritis or respiratory disease, can indirectly cause weight gain by reducing exercise tolerance and therefore activity levels.

Also Read: How To Put a Cat on a Diet

Why Is Weight Gain So Bad?

Cats that are overweight are at risk of developing serious health complications.

Obesity is well documented to contribute to many health conditions and can shorten life expectancy1. Overweight cats are more likely to develop diabetes, arthritis, heart disease, and more. Even a small amount of excess weight can prove detrimental to your cat’s health. It also restricts activity and impacts their general well-being.

Also Read: How To Deal With Food Aggression In Cats

Managing Weight Loss in Cats

Rapid weight loss is very dangerous for cats, so never put your cat on a diet without the help of a vet.

If you think that your cat is overweight, it is important to first seek veterinary advice. Your veterinarian will be able to assess your cat’s weight and body condition and help you develop a weight loss plan if needed. Medical causes of weight gain can be ruled out first, and then they can discuss nutrition and formulate a diet plan with you for your kitty.

Gradual, sustained weight loss is recommended for obese cats. If rapid weight loss occurs, cats can develop a serious liver condition called hepatic lipidosis, due to the liver being overwhelmed by fat metabolism.

The mainstays of weight loss include dietary control and increased activity, once medical concerns are ruled out. Your veterinarian will be able to advise on a suitable food for overweight cats, and how much to feed your cat. If your cat seems hungry, try using puzzle feeders or treat balls to increase satisfaction and satiety after a meal.

It is important to stick closely to their daily allowance and avoid giving little extras. Increasing activity will also help prevent weight gain, perhaps by playing with your cat using interactive toys or those that encourage exercise, such as laser pointers.

Also Read: The 10 Best Cat Slow Feeders & Puzzle Feeders

Weight Gain in Cats: Final Thoughts

A vet-supervised diet and increased exercise can successfully help cats slim down.

Obesity is a common problem in pet cats and can lead to serious consequences. It is uncommon for weight gain to be due to a health condition, and more often is associated with diet, lack of exercise, and neutering. Older cats are also more prone to obesity due to their more sedentary lifestyle and reduced calorific needs. It is important to keep cats at an optimal weight for their health and well-being.

Also Read: Why Does My Cat Steal My Other Cat’s Food?

Frequently Asked Questions

What causes unexplained weight gain in cats?

Weight gain in cats is usually due to their diet (overfeeding) or a lack of exercise. It can also be related to age, with older cats more likely to be obese, or after neutering. Occasionally, a health condition can lead to weight gain, such as via fluid retention in heart disease.

Why is my cat gaining weight but not eating more?

If your cat is gaining weight but their food intake is the same, it might be that their energy requirement has decreased—through age, neutering, or decreased exercise. Less commonly, a medical condition might be causing weight gain, such as via fluid retention in heart disease.

What causes weight gain in older cats?

Senior cats tend to have decreased energy requirements, so can gain weight if they are eating a cat food more suitable for young adults or kittens, who need more calories. Senior cats also tend to be less active, especially if they have a health condition such as arthritis.

View Sources
Cats.com uses high-quality, credible sources, including peer-reviewed studies, to support the claims in our articles. This content is regularly reviewed and updated for accuracy. Visit our About Us page to learn about our standards and meet our veterinary review board.
  1. German, A. (2006). "The growing problem of obesity in dogs and cats." Journal of Nutrition, 136(7), 1940-1946.

  2. Colliard, L, Paragon, B. & Blanchard, G. (2009). "Prevalence and risk factors of obesity in an urban population of healthy cats." Journal of Feline Medicine & Surgery, 11(2).

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About Dr. Lizzie Youens BSc (Hons) BVSc MRCVS

Lizzie has worked in companion animal practice for over ten years, in a variety of roles from small rural branch surgeries to large hospital environments. She also enjoys reading, gardening and spending time with her young daughters. She covers cat behavior, nutrition, health, and other topics for Cats.com.