Anybody with excess amount of skin

You are 21 years old so most likely all or at least most of the skin will take care of itself over time. Skin is quite elastic when you are young and stretches and rebounds. If you lose weight at a safe, reasonable pace, your body will shrink along with your scale reading.

Make sure you resistance train. It doesn't have to be heavy, but you need to rep until it's hard to lift, so people suggest lifting heavy so you're not there all day.
People say a lot about having youth on your side. It depends what you look like now. As a pre-teen, I had a belly apron already, and was covered in stretchmarks. I didn't do much by way of resistance training through the majority of my weight loss, because I knew no better, so I can only speak for myself when i say that a childhood of obesity and over a decade of smoking combined with mostly-carbs and cardio loss didn't do me many favours. I would easily be a size or two smaller in jeans if not for the "leftover" on my midriff.
My boobs have sadly deflated, but some of that is from multiple biopsies on my left breast when i found my tumor. My upper arms are a bit wrinkly like an old person, and I'm only 28.

Even if I was twice as floppy, I'd still do it all over again, because I'd rather be a healthy weight and floppy than full up of fat :happy:
Right now, I'm bulking in hopes of cutting again and losing fat in places I need to, rather than just my flippin' chest. :grumble:

Anyway, sorry for the huge ramble. Just lose slowly, eat well (include much protein) and do a good mix of resistance and cardio. It's the best you can do. :flowerforyou:

I spent hours on youtube looking at people with excess skin and how to prevent it.

1. Lose weight slow (1 - 2lbs a week max)
2. Drink a gallon of water each day
3. Exercise, especially with weights
4. Moisturise every day

You have an added bonus...YOUTH! Your skin should jump back at least 90% if not 100%.