Chinese Oolong tea is categorized somewhere between Green and Black tea. The difference is in the harvest process of Oolong tea leaves. Oolong is only partially dried, and not crushed leaving the whole plant material still intact. This is the primary factor in its health benefits.
I think that even though there is scientific evidence of weight loss agents in Chinese tea, the main thing that pushes along the weight loss is an abundance of liquid intake.
Wu Long is the US Marketed name for Oolong tea. Don't get scammed, there are many companies on the internet making a killing on marketing this stuff. If you've researched any kind of tea for weight loss on the internet, a website for Wu Long Slimming Tea has probably come up in a query or two. These people marketing Wu Long tea are charging 39.99/box, claiming that no matter what you eat or how you live you will lose weight just by drinking this tea. They also claim that you can't purchase it in stores. I almost fell for it and bought some myself, however skepticism took over and I decided to do a little research on it myself. I looked in our local Asian Market and to my surprise I found a product called Chinese Oolong Tea. This tea is exactly the same thing and being sold for .99 cents/box!
Don't get scammed! Do your research!