Here is some information i find it about green tea :
Numerous scientific studies have shown that tea drinkers, specifically green tea drinkers, lose weight faster than those who don’t. According to a study by Abdul Dulloo, from the Institute of Physiology at the University of Fribourg in Switzerland, the plant compound EGCG found in green tea, plus caffeine, increases thermogenesis by 84 percent. Thermogenesis is the generation of body heat that occurs as a result of normal digestion, absorption, and metabolization of food. Green tea also increases your levels of norepinephrine, which prepares your body to burn fat for the "fight or flight"