The only weight you should gain long terms from a breast augmentation is the weight of your two breasts implants combined. There is no physiologic weight gain, except maybe a pound or two shortly after surgery as a result of fluid administered during your anesthesia. If you have gained more than a pound or two in weight six weeks or three months following your breast augmentation the reasons can be many (hormones, dietary changes, less exercise, etc.), but your breast augmentation is not one of them. Don't let "weight gain" be your reason to avoid a breast augmentation if you feel that your quality of life would be enhanced by such. This is the #1 plastic surgery procedure today with about a 98% patient satisfaction. Make sure you consult with an experienced board eligible or board certified plastic surgeon whose aesthetics align with your own when reviewing their before and after gallery. Best of luck to you.