1. Feeding suitable cat food: Choose high-quality and nutritious cat food to ensure that cats get enough protein, fat and carbohydrates. Joy cat food is a good choice, but we should also choose the right cat food according to the specific situation of cats.

2. Add complementary food: In addition to cat food, you can add some other foods to cats, such as cooked lean meat, egg yolk, fish and vegetables. These foods are nutritious and contribute to the health and weight gain of cats.

3. Control the feeding amount: Don't overfeed, and determine the feeding amount according to the weight and age of the cat. You can observe the feces and body shape of cats to avoid overfeeding or underfeeding.

4. Provide plenty of water: Providing cats with plenty of fresh water helps to keep their health and normal digestive system.

5. Regular deworming: If there is a problem with the cat's digestive system, it may lead to insufficient absorption and affect the weight. Regularly deworm cats to keep their digestive system healthy.

6. Reduce stress: cats are easy to lose weight under pressure, provide a quiet and comfortable environment, reduce external interference to cats, and help to gain weight.

7. Increase the amount of exercise: Proper exercise helps to increase appetite and absorption, making cats healthier. Toys, cat trees, activity spaces and so on can be provided. For cats, and increase the amount of exercise of cats.

It should be noted that it takes time and patience to gain weight, so don't rush for success. If your cat is not fat for a long time, it is recommended to consult a veterinarian to ensure its health.