Fat wrap/saran wrap with vaseline?

In the spa, they have a fat wrap where they put oil and vaseline and then they wrap you in saran wrap and you lose inches and a bit of weight. (i understand that you will probably gain the weight back but, i just need to look a little smaller for a party. i read online that you can do it at home by putting vaseline on your body and then wrap youself in saran wrap. has anybody done this before? does it work? and how long do you have to keep the saran wrap on for?