When you have lost weight on your and sag a bit, any exercises to lift them or firm them up??

without getting surgery. Or is it a case of because you have lost weight off there, no matter how much chest work u do they will still be a bit dropsy?? just wondered instead of having to worry bout getting an uplift so they sit up and stay up right...whether the chest work is the go and what sort of exercises to do...if they will give them that result, lifted and firm look?? thanks.