Introduction:
Green tea contains different polyphenols including catechins, epicatechins, epigallocatechin and caffeine. Different studies have examined the effect of green tea with and without physical activity and restricted energy diets on body mass index and body composition. The aim of this study is to systematically review the effects of green tea on body mass index and waist circumference.Methods: This review article was collected by advanced English Search at three databases (pubmed, scopus, and sciencedirect) from the studies published at 2005-2015. After searching with keywords (Green tea AND antioxidants AND BMI/obesity/Body composition) and elimination of similar cases, 83 related articles were picked up and 31 studies (performed on human species) were selected. Finally, 27 articles were checked and 4 articles were removed from the list due to lack of relation.Results: Orally consumed green tea (some with aerobic exercise or supplementation with vitamin E and other polyphenols) in overweight and obese adults (20 studies) within 25 days-36 weeks averagely caused 1-9 kg reduction in body weight, 0.1-5 kg in fat mass, 1-9 cm in waist circumference and 0.4-3 kg/m2 in BMI. Fat free mass was increased significantly about 0.3-3 kg. These changes may be caused by increased fat oxidation, increased sympathic system activity through inhibition of catecholamine-o-methyltransferase and increase of energy expenditure by thermogenesis. Seven studies due to the short period of intervention and inadequate dose of polyphenols and small sample size did not confirm its efficacy. Methods of intervention in studies were in 3 forms: capsules of green tea, drinks and intramuscular injection.Conclusion: Most studies suggest lowering effects of green tea consumption on anthropometric indicators and fat mass and its increasing effect on fat free mass that can be mostly occurred through the increase of fat oxidation, basal metabolic rate and thermogenesis.