Solutions for cats that are too thin but not gaining weight:
1. If a cat is infected with parasites, it will not gain weight. The owner should deworm the cat regularly.
2. If you feed your cat a single diet, it will become thinner due to nutritional deficiencies. Feed a variety of foods, including fresh fruits, vegetables and meat regularly to ensure balanced nutrition.
3. You can feed the cat some nutritional paste, which can quickly supplement nutrients and make the cat fat.
4. If the cat's gastrointestinal condition is not good, the absorption will be poor, which will cause the cat to be very thin. You can feed the cat some probiotics to regulate the gastrointestinal condition.
5. Change your cat to a high-quality cat food that is more palatable and more nutritious to meet the cat’s nutritional needs.