Green Tea
Green tea, also known as epigallocatechin gallate, is part of a large family of chemicals called bioflavonoids that are found in tea, red wine, as well as many fruits and vegetables. Bioflavonoids have antioxidant properties and have been investigated for extensively as possible anti-cancer and cardiovascular drugs. Green tea also contains caffeine which may contribute to its fat-burning effects.
Mechanism of Action
Inhibition of catechol-o-methyltransferase (the enzyme that degrades norepinephrine) possibly stimulates or prolongs sympathetic thermogenesis.
Cell Culture and Animal Models
Fat absorption, adipocyte differentiation and proliferation, lipogenesis, fat mass, body weight were all decreased in laboratory studies. In animal models, plasma triglycerides, free fatty acids, cholesterol, glucose, insulin and leptin were decreased, while beta-oxidation and thermogenesis increased.
Humans
Preliminary studies show decreases in body weight and body fat, along with fat oxidation and thermogenesis.
Interpretation
Green tea extract shows promise as a weight loss agent based on mechanistic studies. Randomized trials are needed to determine efficacy. Longer-term observation will also be needed to determine safety.