Green tea may elevate your metabolism slightly, but it probably won't help you lose much weight no matter how much you drink. In an analysis of six studies published in "The Cochrane Database of Existing Reviews" in 2012, researchers found that on average, people who drank green tea for several months in weight-loss studies shed a mere .04 kilogram -- or 0.1 pound -- more than those who did not.
Green Tea Consumption
If you do opt for green tea, Medline Plus recommends drinking no more than 5 cups per day. In higher doses, the caffeine may cause side effects such as insomnia, headaches, upset stomach and irritability. In severe cases, it can even cause tremors or convulsions -- plus, green tea may block iron absorption from foods. While moderate green-tea consumption is probably OK for most people, Medline Plus reports that supplements are only "possibly safe" and may sometimes cause liver problems. Therefore, you should speak to your physician before taking concentrated green-tea products.