Although green tea does not raise the metabolic rate enough to produce immediate weight loss, a green tea extract containing polyphenols and caffeine has been shown to induce thermogenesis and stimulate fat oxidation, boosting the metabolic rate 4% without increasing the heart rate.
Green tea has conquered the world thanks to its unique properties: it contains a high concentration of antioxidants which help protect the human body from free radicals that adversely affect our health. Green tea is a rich source of vitamins, minerals, valuable essential oil, and flavonoids; we traditionally associate it with longevity.
Green tea and its extract have been shown to fight obesity and lower LDL "bad" cholesterol -- two risk factors for heart disease and diabetes -- but in very limited studies. One study in the Netherlands and a study in Japan showed that green tea did both.