Hi Nicholas
It is true that oolong tea is being used in research in relationship to obesity. I think it is also true that there are website that try to capitalize on this fact by over hyping Wuyi Oolongs, and selling poor quality teas for high prices on their sites. It is true that the are a lot of Wuyi oolongs that sell at pretty high prices, but it is not the case in the quality of tea being sold for weight loss.
Tea in general is good for weight loss in that it helps to keep blood sugar stable. It is thought that oolongs help by binding to some fats, the Chinese believe that the more a tea is oxidized the more warming and thus the bigger the aid to digestion.
It is probably good to drink 4 cups a day or more. The Chinese usually drink tea after a meal, though they will be sipping tea through out. You will notice that if you have a cup of tea after a meal it will take away any bloated feelings you have from the meal.
I hope this is helpful.
Austin