Green tea contains caffeine. A cup of green tea contains around 24-40mg of caffeine compare to 100-200mg of in cup of coffee.
Caffeine is the stimulant which increases the metabolic rate of the body so by which the rate of fat burning increases in the body.
Green tea is also loaded with range of antioxidants called as catechins. One of the important of these antioxidant is EGCG (Epigallocatechin gallate). This antioxidant increases the metabolism. The EGCG inhibits the enzyme which breaks down the hormone norepinephrine. So that levels of hormone norepinephrine increases. Function of this hormone is to tell adipose tissue to start breaking down fat. So increased levels of norepinephrine sends stronger signal to adipose tissue which leads to more fat break down.
Both caffeine and EGCG have synergetic effect which leads to fat loss.
These benefits can be obtained by drinking green tea or taking green tea extract tablet.