It seems kinder to remove a dog's desire for aggression and/or mating rather than prohibiting them to act upon it. This does create a calmer animal. As far as the weight gain, you should be looking into proper nutrition and diet anyway. Once you feed him according to his weight and nutritional needs, it is easily modifed and maintained. One of the only ways to be sure your dog is healthy, is by the consistency in his diet. Good luck