Significant weight changes can alter the appearance of augmented breasts, because the breast contains fat that changes with your overall weight while the implant stays the same size.
Weight gain
Added breast fat can make the breasts larger and change their shape and proportions relative to the implant.
Weight loss
Loss of breast fat can make the implant more prominent and palpable, increase visible rippling, and reveal sagging.
Why stability matters
Because of this, surgeons usually advise reaching a stable weight before augmentation and maintaining it afterwards for the most predictable, lasting result. Major future weight changes (or pregnancy) may prompt a revision.