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Why is my cat overweight?

20 January 2018
Going back 30 or 40 years, cats in the UK did not get overweight. They were probably just as loved and cared for then as now, but they were slimmer. Historically, “Appetite is an expression of physiological need,” was another way of saying that cats only eat as much as they need to keep going – they would not eat to excess and get fat.

The fact is that now many cats are significantly obese, and most are probably at least moderately overweight. Back in the 1970s the average UK cat weighed about 4kg. Now it is about 5kg.

So what has happened? Why is there a difference? Why are cats so much fatter now than they were a generation ago? Almost certainly this is mostly down to the food we give them. 

Their natural food would be uncooked whole rodents, small birds and the like. They would eat most of the carcass of their smaller prey – skin, bones and the rest. Domestic cats have always hunted to some extent. In the past they were often given the commercial cat food of the time, as well as scraps and treats – usually fresh meat or fish. Commercially prepared cat food in those days was tinned fish, though cheap meat was used too. Vitamins and minerals were added. The food was always wet, not dried, so it would have been about 80% water in fact. It also did not contain much carbohydrate. In the late 1970's the dried, “kibbled” cat foods came out. They were cheap to produce and very palatable. Interestingly, kibbled foods is difficult and expensive to manufacture without adding cereal products to the mix. It was soon discovered that tasty kibbles could easily be made by including cheap cereal in the ingredients, so that started to happen. Since then, it has happened a lot. The dried cat food market is now worth billions of pounds every year.

There are probably lots of reasons why cats are fatter now than in the past, but it will mostly boil down to the fact that they eat more. The carbohydrate content of modern cat food is unnaturally high. A mouse contains very little carbohydrate; a bowl of kibble contains lots.

There is something about carbohydrate which affects the feeling of being full. Ideally cats should eat when hungry and stop when they are not. When food is not needed, it is best not eaten. However the job of cat food manufacturers is to make food which is eaten in the largest possible quantities. Therefore they need to encourage food to be eaten beyond the point when the genuinely required amount has been consumed. Many older people will remember the cat food adverts telling us that “8 out of 10 cats prefer it.”

There is huge competition for cat food manufacturers to make a diet so tasty that cats will eat it when it would be better if they just walked away. Few people continue to buy a cat food that their cats do not eat. Most people try a different food, which they hope will be tastier, then feed it to the point that their poor cat cannot manage to eat any more!

If their cat starts walking away from the food before eating the whole lot, their owner looks for an even tastier food to give. No wonder cats are fat!

Many people with a ‘hunter’ cat will observe that their pet cat will kill mice or voles, but then not eat them. They are often presented as little presents by the back door. This is mostly because cats enjoy hunting, but the idea of eating a mouse is about as appealing as a good salad is to the average teenager. Why would the cat eat the mouse, when there is all that lovely cat food waiting in the kitchen? 

So what is the answer? In a way it is simple, but in practice it clearly is not. The latest developments in cat food are looking to reduce the carbohydrate content. As an owner it is better to provide cats with good quality food in limited amounts twice a day and expect an empty plate at the end of each meal. Low carbohydrate food would certainly be more natural and would reverse the change that has been happening in cat food over the last 30 to 40 years.

Fussy cats are extremely common now, but it is also worth noting that a fussy cat is nearly always the product of the feeder, not the cat or the food. They become that way by repeatedly being offered more food than they can eat! So they pick out the best bits, leave the rest, and come to expect the most tempting food every time. Fussy cats are virtually always overweight. The answer is to significantly reduce the amount offered, stick to two meals per day, and assume that unless they are showing signs of being ill, any leftover food is clear evidence of being given dramatically too much food. That should never happen with any cat that is needing to lose weight.

Did you know… that feeding your cat just three cubes of cheese is like you eating two double cheeseburgers! 

Pet obesity is a growing issue that affects millions of UK pets. Up to 40% of pets in the UK are thought to be overweight or have obesity.

If you are unsure what to feed your cat, or are concerned about their weight, your first port of call should be the vet or vet nurse, who will be able to advise on a healthy regime.

The Body Condition Score (BCS) system is a standardised way of assessing the weight of different pets. It uses a scale ranging from 1 (very thin) to 5 (obese) to represent different weights as body shapes. Getting your cat checked over regularly by a vet is a great way to help them stay fit and healthy. As well as weighing them, your vet can check your cat’s BCS, which can help to identify the early signs of weight gain.