I have read somewhere that with Dogs, bitches can gain weight after being fixed not too sure about the Male Dog though, I never had my two German shepherd bitches done & they both made it to twelve & thirteen, German shepherd dogs can suffer with hind quarter problems so extra weight would have been a no, no… That’s why I never had them done, for fear they would gain weight & incur hip problems in later life, as it happens they both died in their beds from natural causes…. Up until their final illness they were both still very agile… :-/