Tackling Feline Obesity

By Dr Joanna De Klerk

Ever thought that a chubby cat looks kind of cute? Well, regardless whether or not a cat looks cute, piling on the pounds can cause serious health consequences.

Maybe your cat is on the larger end of the spectrum, and you’re wondering if they need to be put on a diet? It can be overwhelming when it comes to figuring out how to do that, and what their the ideal weight is.

What is Feline Obesity?

Approximately 50% of middle aged cats are either overweight or obese. With so many cats larger than optimal, our social media platforms are flooded with pictures of cats that need to shed some weight. As a result, it’s easy to think overweight cats are the norm, and we lose sight of what a normal weight cat really looks like.

When we think of malnutrition, we usually think of skinny animals. However, obesity is also classed as malnutrition. A cat which is between one and 19% above their optimal weight is classified as overweight, and over 20% is classified as obese.

Feline obesity is not a benign condition. It can predispose to many different diseases. In dogs, it has been suggested that over two years are knocked off their life-expectancy due to being overweight, and we can assume the same in our cats too. That’s almost 15% of their life!

In addition to that, fat is not an inert body tissue. It secretes inflammatory hormones and creates oxidative stress in the body. In other words, an obese cat’s body is constantly inflamed. 

What Causes Obesity in Cats?

Naturally, cats are meant to only eat their energy requirements in food, and not more. In other words, when they have a lazy day, they know to eat less, and when they exercise more, they eat a greater amount. This is because of a hormone called leptin. When released by the small intestine and fat cells, it inhibits hunger. However, some studies have suggested that despite overweight cats having increased levels of leptin, they continue to overeat and gain more weight, suggesting a condition called ‘leptin resistance’. 

Therefore, cats who graze their food are more likely to put on weight, as their food intake is not controlled. They don’t have a natural ‘shut-off’ switch for their hunger levels and don’t know when to stop. And the thing is, the food is continuously there for them.

In addition to the problem of grazing, and ‘leptin resistance’ predisposing to obesity, there are also other factors which can lead to obesity.

When a cat is neutered, their metabolic rate decreases by about 20%. This means they don’t need as many calories to still maintain their normal bodily functions. In addition to that, breed and genetics play a role too. Purebred cats are more likely to be lean, whereas moggies are more likely to be overweight. 

Finally, activity levels also play a huge role in managing weight. Outdoor cats roam and hunt more than indoor cats, resulting in a higher expenditure of energy. Therefore, indoor cats are more likely to end up overweight than outdoor cats. 

Body Condition Scoring

So what weight should your cat actually be? Putting a figure on it is not easy. For some cats, 5kg would be fine, whereas others, 5kg would be morbidly obese. Therefore, a scientific method called ‘body condition scoring’ has been developed to help you keep track of your cat’s body weight.

Body condition scoring uses a scale of one to nine, or one to five. The one to nine scale is more common in domestic animals. A score of five or just under is ideal. Every point on the scale is a movement in weight by 10%. So for example, a cat which is body condition seven is 20% overweight.

Body condition scoring is based on the ability to feel the ribs and the spine, as well as the general fat coverage over the body. The following chart is free to download from Royal Canin and gives and excellent overview of each body condition score:


Your vet can be a very valuable resource to help your kitty lose weight, as it should not be done without the oversight of someone knowledgeable. When you first take your cat to the vets to discuss weight, he will determine your cat’s body condition score for you, and work out what your cat’s ideal weight is. He can also provide you with plenty of advice how to achieve their optimal weight, and over what timeframe that should happen.

What are the Health Risks Associated with Feline Obesity?

Obesity can lead to a number of health implications. Not only does it reduce your kitty’s lifespan, it can also result in a higher chance of developing the following diseases and complications:

  • Diabetes mellitus
  • Urinary tract infections
  • Osteoarthritis
  • Skin diseases
  • Hepatic lipidosis 
  • Breathing problems
  • Decreased immunity
  • Increased anaesthetic risk

That’s quite an incentive to encourage your feline friend to shed those excess pounds!

How to Put Your Cat on a Diet

So, you’re probably wondering how to start with putting your cat on a diet. Dieting appropriately is very important, as a rapid weight loss can lead to a condition called hepatic lipidosis. This is when fat is mobilised from where it is being stored around the body, to be used as an energy source when calories are low. However, there ends up being too much fat in the blood due to this mobilisation. As a result, the liver mops up the excess and stores it, which when severe can lead to liver failure. Weight loss is a marathon, not a race. If your cat is obese, it might take up to a year to reach her target weight without causing hepatic lipidosis.

Your vet can draw up a suitable weight loss plan for your cat, which details how much weight she should be losing, how much food she should be consuming, how much exercise she should do, and how quickly it should all be happening.

Your cat will need to change her food to ensure she loses weight. Some people put their cats on a diet by feeding them according to the guidelines for their optimal weight instead of their actual weight. And other people simply decrease the amount they are feeding their cat by 5-10%. Unfortunately, neither of these options are fully effective, as it leads to your cat becoming extremely hungry.

A veterinary prescription weight management diet is a better option. These diets are nutritionally balanced, low in calories, low in fat, and high in fibre. As a result, they make your cat feel fuller for longer. The top three veterinary prescription weight management diets in the UK are:

  • Hills® Prescription diet metabolic
  • Royal Canin® Satiety Support Weight Management
  • Purina Overweight Management®

It’s important to be accurate with your feeding. Follow the guidelines on the packet, or your veterinarian’s advice, and weigh out your cat’s food every day. This means you won’t provide more than her 24 hour allowance. Remember treats contain calories. Ideally, you should only give your cat the diet food, however if she simply can’t go without her daily Dreamies®, then remove some of the allotted food for the day to make up for those calories.

Weigh-ins at your local vet are the key to success. It will keep you accountable for your cat’s weight loss, and boost your morale by seeing the weight drop off. Weigh-ins should be every 2-3 weeks, and most vets will allow you to come into the practice to weigh your cat free of charge.

How to Maintain an Optimal Weight

Congratulations if your cat has achieved her optimal weight!

Once you’ve got there, it’s important not to go back to your cat’s old feeding ways otherwise she will quickly gain weight again. You might not notice it at first, as subtle weight increases often are not initially visible, so continuing with the weigh-ins is vital.

Portion control is the key to maintaining your cat’s weight. You should continue weighing out her food daily, so that she doesn’t get more than she needs. It is also a good idea to keep her on the diet food, or switch to a ‘light’ food, rather than changing her diet back to the old food she was on.

Take Home Message

Feline obesity is such a common problem that we’ve become immune to what a fat cat looks like. However, obesity is not something to become complacent about. Your feline friend will thank you endlessly for improving her health by ensuring she is an optimal weight. And by seeking professional advice sooner rather than later, you can ensure your kitty lives a healthy, long life.