building muscle can help u using energy, so that it can help u to be slimer, and 3lbs of muscle = 1lb of fat (size), although u may seems heavier, but actually ur healthier.
and building muscle will let ur whole body shape more beautiful, instead of one part.
for the reason of my broken arm, i stopped to have exercise, i even gym regularly, go, having exercises, u will get even healthier, but not only slimer.