I bought this item about two weeks ago. I use the second zipper and use it for the whole day and it does make you sweat a lot. I haven't measure my waist but I can see that is slimmer and other people noticed too and it is not a small change, is a big difference. Is a miracle worker for so little money, now everybody around me wants one too. The only thing is that it does look bulky under clothes, people can totally tell that you have it under your clothes unless you have lose clothes not tight. I totally recommend the product!