I think that loose skin is something that is on all of our minds when losing weight. But I totally agree with previous posts that getting your weight under control is far more important than the loose skin.
As Jon says, you can buy all sorts of undergarments that will remedy the problem but there is no underwear in the world that can protect you from diabetes, heart disease or any other of the weight related illnesses that you would be prone to if you didn't do something about it.
Also if you are fairly young the skin retains a lot more elasticity than the skin of somebody older. (I know because I'm in the latter category.) So try the diet and good luck. you will get plenty of support and encouragement on this forum. I know as I'm a newbie myself and reading everybodies tips and stories has helped me enormously.
So come on in. You've nothing to lose but your excess weight.
Best wishes. Pat.