Diabetes is the next reason a healthy cat could also be losing weight. Its the result of a benign hormone-producing tumor on the thyroid gland which elevates levels of the thyroid hormone. Actually these cats do not lose fat.
The important thing is to know when to see a vet and how to change their diet if needed. Ad Is Your Cat Overweight. We had her thyroid checked and it is normal. There has to be something missing as she can eat 4 to 5 small cans of cats food a day and is still hungry.