Will my skin firm up if I lose about 50 lbs? I just turned 21 years old?

Right now I weigh about 225 and wear a size 16/18. I'd like to get down to maybe a size 10/12. I'm thinking that'll be around 170 lbs or so. Anyways, will my skin firm up? I plan on doing it by eating right and exercising over the course of a year or so. I've been overweight all my life so my skin has never really been tight. I have a lot of stretch marks which I know will not go away. I just want to know bad the damage is gonna be if I get skinnier. Am I young enough to still have elasticity in my skin?
Will my skin firm up if I lose about 50 lbs? I just turned 21 years old?
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