I'll tell you this from personal experience....
I lost 100 lbs. and much of it was around my gut. That's where I hold it. Also, I'm only 5'6" so that's a TON of weight.
My skin didn't tighten up very much at all until I got under 10% body fat. You hear people say that, but you don't really believe it. Oh, and don't fool yourself, 10% is pretty dang low... you're probably not there yet even if you think you are. The honest truth, and I truly believe it, is that most of your skin will and can tighten up IF you get to low body fat.
I could literally grab and pull skin out 6 inches. It was there in globs. It was horrible.
Upon getting down to about 8%, things really started to change. I noticed almost weekly changes and tightening. The other thing that surprisingly helped, and I wasn't much of a believer, was tanning. I started to tan because I was going out of town and was going to spend a lot of time in the sun and was white as hell and didn't want to get burnt. I started going and got pretty tan. I really did notice that my skin tightened up even more during that process. Maybe it was luck or coincidence, but I don't think so. I always saw a few posts about this and completely wrote it off as utterly ridiculous, but sure enough, it did help with me.
My advice, get your BF checked, even if you have to do a hydrostat (which is the most accurate). If you do skinfold it will read higher if you have lose skin.
I continually though I should see improvements and thought I was low BF, but wasn't. When i got down there, it tightened up and still is slowly.
Oh, I'm 28 years old. Also, I have huge 12 inch stretch marks on my stomach... they've gotten tremendously better, but they'll never go away. They are pinkish, which some people say means there's hope, but they've been like that for a couple years and I don't see them changing. Tanning also helped that too.
Anyway, there ya have it. That's my story and I'm sticking to it. Creams, etc never worked either and I tried them all.
PM if you have questions, etc. GOOD LUCK, I understand it can be a VERY frustrating thing, especially when you work so hard and your want to look your best but you just can't.
http://www.54thavenue.com/mine/thumbnails.php?album=1
Yes, I realize there aren't any pics with my shirt off, but I'm still struggling a little bit with how my body looks and am a bit squeemish... FYI -- that last pic of me makes me look twig thin. I'm really not... it's the angle.. really...