The main reasons why cats do not gain weight are: congenital genetic reasons, gastrointestinal problems, and the cat is still in the developmental stage.

1. Innate genetic reasons:This is the same as some people in humans who cannot gain weight no matter how much they eat. Some breeds of cats can also eat for a long time without gaining weight. For example, Siamese cats, Bengal leopard cats, and Chinese garden cats (excluding Daju), Yang Yang, owners of these breeds of cats only need their cats to be well-proportioned.

2. Cat gastrointestinal problems:If the cat performs well in terms of appetite and has no mental problems, but does not gain weight for a long time and is accompanied by vomiting, diarrhea, etc. from time to time, Then it may be that there is a problem with the cat's gastrointestinal tract. It may be that their gastrointestinal tract is sensitive and has poor absorption, so they have not been able to gain weight. If this happens, please take good care of the gastrointestinal tract under the advice of a doctor.

3. Cats are in the developmental stage: Generally speaking, cats are in the developmental stage when they are two to eight months old. During this period, they are energetic, have a wide range of activities, and have high metabolism. It's big, so it's normal to eat for a long time without getting fat.