Chinese researchers claim that "the polyphenol compound in tea - especially Oolong tea - can help obese people battle the bulge."
The research was part of a 5 year study looking at genetic causes of obesity.
Oolong (or wulong) tea sits somewhere between green and black tea in terms of fermentation. Black tea is fermented, Green Tea is unfermented, Oolong is semi-fermented.
Unfortunately the above research does not appear (yet) in an English medical journal - so we cannot delve into the details.
There is, however, a large body of research surrounding tea, - in particular its anti-oxidant properties. The Oolong Tea website points to various studies showing a possible connection between tea drinking and fat metabolism.
Polyphenol is a type of antioxidant found in fruits and vegetables like blackberries, cherries, grapes, cabbage, broccoli, and celery, and other plant foods, including red wine, chocolate, tea, olive oil, and whole grains.
In many ways the health claims are similar to that of Green Tea - a healthy drink to be sure - but no miracle weight loss cure. I suspect that you would also need to be drinking considerable amounts of the tea to obtain any benefit, which flies in the face of tradition. Oolong tea is typically enjoyed slowly.
So it is unlikely we'll see an Oolong tea craze anytime soon, especially since Oolong tea accounts for less than 2% percent of the world's tea production; black tea (78%) and green tea (20%) are most the popular.
Also, black tea and green tea are consumed in many parts of the world, such as Western countries, the Middle East, South Asia, China, and Japan, where as Oolong tea is mostly limited to southeastern China.
But if you drink Oolong tea, your best bet is to drink tea without milk, and avoid all the ready-to-drink tea and sugar mixes that are available.