Few is right
According to the only published study, if you drink 4 cups of green tea every single day, you can lose 8 pounds in a year. Results were seen with real tea, not green tea extracts or supplements.
It's worth it to drink the tea for the antioxidants.
Also, drinking a cup of tea can help you keep from eating other foods with calories, by providing comfort or other satisfaction. So it can really help that way.