It is VERY possible to lose lots of weight and avoid lose skin and plastic surgery. Do your research, talk with your doctor and commit to it.
I've lost 130+lbs on my own through exercise and had no lose skin, gain back 60 of that and going through the lapband, I've researched and have found that the balance of protein and exercise will prevent lose skin and the "need" for plastic surgery.
Everything is not about the number, it's about how and what you lose. You may lose 100lbs but was 50 of that muscle? If so expect to have lose skin. You want to eat as many grams of protein as what you want to weigh. Your muscles feed off of the protein and help burn the fat dropping which is what causes what people call "excess skin."
If you really research it, you'll come to find out there's no such thing as "excess skin" - our skin is designed to grow and shrink with us (yes even after we have "strech marks") if our skin wasn't so resilent we wouldn't have the ability to have stretchmarks, our skin would just rip once we got too big.
Here's some sources:
The Myth of Loose Skin
Avoid Loose Skin After Weight Loss
Tighten Skin After Losing Weight: Quick Weight Loss Leaves Loose Hanging Skin | Suite101.com
Etc... just google and you'll find it.
I have the good fortune to have fitness experts and bodybuilders as clients, they embark their knowledge on me constantly. I've seen a man go from over 400lbs to 235lbs of lean muscle with NO loose skin among others.. Research, exercise, stick to the plan and keep your protein up and you too can avoid excess skin.