First of all, yes, you'll have excess skin problems. But that is easily fixable (by an operation). There is no way to avoid it.
The second thing i wanna tell you is: don't do it to yourself!!! Change your lifestyle. Start eating a healthy and balanced diet, exercise, and you'll see it will work like magic.
If you fast, you'll lose weight too fast and then you'll gain it all back once you're back to eating.
It's shocking for your body! Your body will start burning less calories because it will get used to the fact it needs to save it because you don't feed it.
It's the worst thing you can do to yourself.