No. It is a common misconception that cats automatically gain weight following a spay/neuter procedure.
However, the weight gain many owners may see is the result of several factors. Often cats are spayed or neutered when they are young and still growing. As their growth rate slows, they require fewer calories. Therefore, you need to decrease the amount fed to your cat each day as it approaches adult body weight. Neutering your cat may also result in a change in metabolic rate so that it doesn't require as high a caloric intake. Also, by spaying or neutering your animal, you may see a decrease in some behaviors that expended a lot of energy. Roaming, behavioral signs of estrus, and other mating-related behaviors will decrease so that your cat will require fewer calories as well.
Put simply, your cat will not gain weight as long as you feed it a balanced diet and provide regular exercise.
