I been contemplating fixing my dog. My concern is that she is kind of older now. 6 years old. She had two litters which were accidental and though we embraced the litters with love. its trying on the owners and the dog. My main concern is i dont want her to change in temperament or anything like that. Does it change the dog? i also heard they might gain weight and thats the last thing she needs shes already chubby.