Hi,
I'm 27 lost around 4 stone so far and i hae no sagging skin at all phew !! ( must admit boobs have lost the fullness but i dont mind that),
the only exercise i did was walking walking and more walking, also i did do 100-200 sit ups really need to start those again, so not sure if it helped or i am lucky or just young enough for it to bounce back,
don't let it worry you too much x
good luck with your journey
S x