It is common for cats to gain weight after they are spayed or neutered. However, if your cat is still young, say less than 2 or 3 years old, it should still be quite playful. If your cat is sluggish or doesn’t play like it used to, take it to your veterinarian for a checkup. While serious health problems are unlikely, the possibility should be ruled out.
If everything is all right, then a different diet is probably in order. Gradually switch your cat to a formula designed for less active or overweight cats. Diets for less-active cats generally have somewhere between 10 and 14 percent fat, while weight-reducing diets may be less than 10 percent fat. In addition to providing a clean bill of health, your veterinarian can also recommend the appropriate diet to feed your cat.