I have 23% body fat (which for my age is on the lower side of the healthy scale) and Caroline is right, the parts of me where I don't have loose skin looks ok and toned but my tummy, legs and arms have a bit of loose skin, not loads and you can't tell at all when I'm in clothes but it is there still.
I just tell myslef that it's better being loose and empty than being full of fat.
My old Lighterlife counsellor has surgery to get rid of her loose skin and advised to only do it if you are really so so down and depressed about it as puts your life on hold for a few weeks and also hurts so so bad.
I wont ever have surgery for vanity reasons as I don't personally think all the pros outweigh the cons for me as I am not down about my slightly loose skin.