I don't know about the green tea part, but it seems to me that if you are drinking a significant amount of water with either a capsule or tea bag, you will fill yourself up faster and not feel as hungry. That alone should help slightly with weight loss.
I have heard about green tea's benefits, so I try to drink that at work whenever I am cold and need something to warm me up. It helps that I'm not a daily coffee drinker anyway!
