Since spaying and neutering removes the organs producing sex hormones, there is a change in metabolism. This change is similar to a person growing out of their teenage years. Because the metabolism has changed, the amount of calories taken in needs to be changed too. Spayed and neutered pets that are overweight or obese is the result of overfeeding, not the surgery. By regulating your dog's diet and caloric intake, you can prevent obesity in your pet.