Hoodia seems to be working for me for weightloss, too good to be true?

My wife and I saw a special on good morning america about Hoodia Gordonii Dex-L-10 and a MD talked about how he fully expected it to not work but did a month long study on some volunteers and they all lost weight and he was very surprised and even took it himself and lost weight. So I ran out and got some a couple days ago and i'm down 2 lbs and my wife is down 2.5. Is it too good to be true? I also understand Pfizer is trying to make a prescription out of it. It seems too easy.