Honestly i do not think it changes their personality.
Yorkies are tiny dogs. They are usually finished growing at 1 year old, most of them before that. with females i spay at 6 months before first heat. with males, depending on the breed, i will wait till they hit their maturity age (sometimes 2 years old with giant breeds) before neutering as long as they are not displaying behaviors i do not want (aggression, marking, craziness for females, etc). with dogs as small as yorkies, i would get them fixed at 6 months regardless of maturity age because they typically don't grow much more after that. I had my female spayed at 6 months and she did continue to grow and fill out. she was less then 3lbs at 6 months old and at 1 year she was between 4 and 4.5lbs. now at 4 years old she is just under 5lbs and still in perfect physical condition (actually on the skinny side). With large breed dogs i think you definitely need to let them reach their "growth potential" so they don't have any problems with their bones and joints later on.
The only reason for your pet to gain weight after spay/neuter would be you feeding them too much. yes their metabolism changes, but that happens with age anyway. Sometimes their energy level does change too but again that can change with age anyway. Mine were always still just as energetic afterwards. If you notice your dog gaining weight, then just cut back on the food a little. no biggie.
__________________ Kellie  and  Morgan |