According to an analysis in the British Journal of Nutrition green tea does have a supporting role in weight loss but it is unsure about how much impact it actually has (Thavanesan, 2011).
In essence, this means that there was some differences in weight-loss between the study and control group but the results were not huge. There could be some potential problems as they are related to compounding variable and other factors.
Should you buy or not buy?
It doesn't appear to hurt to purchase a green tea extract. It doesn't mean that you will have significant weight loss as a result but as one of the many supplements available it has the potential to be beneficial. I would suggest that instead of a supplement you just get into drinking green tea naturally.
Thavanesan, N. (2011). The putative effects of green tea on body fat: an evaluation of the evidence and a review of the potential mechanisms. British Journal of Nutrition, 106 (9).
Articles may be distributed with attribution to authors Murad Abel