My cat becomes very thin Why?

Weight loss is a sign that may be indicating that our cat is in the initial stages of some disease. It is a symptom that we have to pay attention to.

If you appreciate that you are losing weight despite eating properly, these could be some of the causes.

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Weight control in our kitten

Cats usually stay at the same weight throughout their lives, but there are some stages in which it can undergo variations that will need to be controlled. They are as follows:

  • Growth stage: during the first months of life, cats have to gain weight at a considerable speed, since by six they already have practically their adult body.
  • Aging stage: approximately 7-8 years old, cats can suffer from age-related pathologies that will affect their weight, reducing it.
  • After sterilization: both cats and queens after this intervention reduce their energy needs so that they will gain weight if we feed them in the same way as before surgery.

In these periods we can weigh our cat at home regularly. To understand the data we collect, it is important that we take into account the proportion. If our 3 kg cat has lost 300 grams, even if it seems little, in reality, he will have lost 10% of his total weight. This would be as if a 70-year-old person had suddenly lost 7 kg.


My cat loses weight from not eating

Before thinking about a disease we must know that if we change the cat’s diet, it may simply not like it and that is why it refuses to eat. To avoid this, all the modifications in the diet must be made gradually and, if the cat still rejects it, we will have to go back to the old way.

This works even for sick cats that need a specific diet. If they do not want to eat it, it is better for them to continue with their usual food than to stop eating food completely. We can also make use of some nutritional supplements suitable for cats, to increase the flavor of their food and make it more palatable.

Mouth problems in cats

Cats can suffer from diseases in the mouth such as gingivitis, that is, inflammation of the gums, tartar, etc. These pathologies are usually accompanied by intense pain that will make the cat stop eating and thus lose weight. In some, we will detect hypersalivation.

These cats may ask us for food or eagerly approach the feeder, finally not even being able to open their mouths. They need urgent veterinary attention. We can also suspect an oral problem when the cat leaves small fragments of food on its plate.

Digestive problems in kittens

There are diseases that affect the digestive system that can lead to weight loss and, usually, more or less frequent diarrhea or vomiting. They are pathologies such as inflammatory bowel disease, malabsorption, intolerances or food allergies, etc.


Cancer and infectious diseases in cats

The appearance of tumors can also be behind the loss of weight of a cat, as one of the signs in the early stages of the disease. More common in elderly cats, in the only weight loss is already a reason for veterinary consultation, precisely because early treatment improves the prognosis.

Immunodeficiency and feline leukemia are viral diseases that have no cure and can present with many different symptoms. They affect the immune system and favor the appearance of tumors. They can make the cat lose weight.

The importance of stress

In addition to physical causes, a cat under stress can lose weight. Sometimes it will be because he finds an impediment to access the feeder, for example, another cat with whom he fights or someone who bothers him.

There are multiple triggers of stress in cats since these animals are very sensitive to any alteration of their routine. Some will be obvious, such as a move, the arrival of a new member of the family, works, etc. On the other hand, others will go unnoticed.

It is important that we try to discover the trigger to solve the problem and whenever we are going to make a change that affects the cat we must introduce it gradually to minimize stress.

My cat eats a lot but loses weight

Most caregivers are concerned when their cat stops eating because they interpret it as a sign of illness, but they do not consider weight loss a reason for consultation if the cat continues to eat. It is a mistake that can cause a visit to the clinic to occur when the disease is already advanced. Some of these diseases are the following:

  • Diabetes mellitus: affects cats of middle and advanced age, generally overweight. It is due to a deficit of insulin, which causes the level of glucose in the blood to rise. In addition to losing weight, even if they eat, we can notice that they drink a greater amount of water and, consequently, the amount of urine they eliminate also increases.
  • Hyperthyroidism: common in cats older than ten years. In this disease, there is an increase in the secretion of thyroxine excreted by the thyroid gland. This increases the metabolism and therefore the cat increases its activity and loses weight even if it eats.

My cat drinks a lot and loses weight

The appearance of these two symptoms together should always be a cause for concern because they are usually associated with chronic kidney disease, which is more common in older cats. It is not curable but it is treatable.


The kidneys can be damaged and continue to function without showing symptoms for a while because they are able to compensate. Only when the damage is widespread will we see symptoms beyond the weight loss that usually begins a year earlier.

Since it is very important to initiate early treatment in this type of disease, we insist on the need to go to the vet even if we “only” perceive that the cat is losing weight.




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