It's generally recommended that a kitten be neutered before it is five months old, according to the ASPCA, but it's safe to neuter kittens as young as eight weeks. Many animal shelters follow this practice in order to sterilize kittens prior to adoption.
The ASPCA advises that fixed male cats may require fewer calories, but contrary to popular belief, a cat that has been neutered will not become overweight or lazy when fed a proper diet. Neutering at a young age may prevent a male cat from roaming and marking its territory by urine spraying.
Neutering has other benefits, according to KittenCare.com. Male cats don’t call or howl persistently to find a mate and are less aggressive and more affectionate. Neutering also increases a cat’s longevity.