I'm afraid to spay my dog because I've heard it will make her fat and lazy. Is this true?
There has been no scientific evidence demonstrating ANY behavioral change in spayed/neutered dogs, either for the better or worse. Spaying/neutering may reduce the sort of sexual behaviors that can be problematic (like wandering, marking, humping, etc.) or keep them from developing but it will not make a dog more aggressive, more mellow, fatter, lazier, less intelligent, less driven, etc. All accounts of this happening are anecdotal and probably could be met with an equal number of observations of no reaction or reactions in the opposite direction - except those never get passed along by word of mouth. Ever have someone come up to you and say "Guess what?! My dog got spayed and her behavior didn't change at all!"? Probably not but it happens all the time.