Weight loss can help if the underarm fullness is mostly general subcutaneous fat and you are still above your stable goal weight. It will not reliably correct loose skin, axillary breast tissue, or a defined fold that remains after surgery. In the visible photos, there appears to be fullness and folding along the lateral chest/underarm area, but an exam is needed to tell how much is fat, skin laxity, or breast/axillary tissue. At 1 year post-op, most swelling has settled, so it is reasonable to have this assessed if the area still bothers you. If the issue is mainly fat and the skin has good tone, targeted liposuction may help. If there is loose skin or firm axillary breast tissue, direct excision or a scar extension may be more effective than liposuction alone. It is best to be near a stable weight before revision planning, because further weight loss can change both the fullness and the amount of skin laxity.