text: Yes it can.  Contrary to one of the answers above, caffeine generally boosts the metabolism.  I've been taking it for years myself and it definitely has a beneficial effect on your body, stimulating your metabolism and brain. \n\nhttp://thyroid.about.com/cs/dietweightloss/a/greentea.htm\nhttp://www.findarticles.com/p/articles/mi_m0846/is_12_23/ai_n6125798\nhttp://www.preventdisease.com/news/articles/022406_green_tea.shtml