Green tea may have specific weight loss effects in humans and other mammals. In particular, green tea contains methylxanthines including caffeine, that may stimulate the central nervous system and induce weight loss through the release of catecholamines. These catecholamines bind to receptors on cells and induce lipolysis and fatty acid oxidation. However a number of other substances contained within green tea may also have weight loss effects. In particular, both the catechin polyphenols and the amino acid L-theanine, may act synergistically to increase fat oxidation. Caffeine is known to increase fat oxidation and a large body of evidence supports the fat oxidising effects of caffeine in mammals. However, much less is known about the mechanisms and effects of catechins and L-theanine, with regard their effects on weight loss. Therefore a number of studies have looked at the effects of decaffeinated green tea in order to elucidate any contribution made to weight loss by the non-methylxanthine components of the tea.
Green tea has been shown to induce fat loss in subjects without the requirement for energy restriction of physical activity. That these effects are seen following administration of green tea extracts that have been decaffeinated, suggests that other components in the tea are responsible for these effects. One compound that is suspected of causing weight loss is (-)-epigallocatechin-3-gallate, a flavonoid belonging to the catechin subgroup. Around 5 cups per day of green tea or the equivalent amount of catechins in a supplement (~850 mg (-)-epigallocatechin-3-gallate) has been shown to be effective at reducing body fat percentage in overweight women. The effects are small, but green tea is an effective fat oxidising agent that can be used with other dietary strategies.
For example, in one study, researcher administered decaffeinated green tea to a group of overweight women for 12 months. The green tea extract contained 843 mg of the catechin (-)-epigallocatechin-3-gallate (equivalent to 5 cups of brewed green tea). There was no mention of L-theanine in the study, but it can be assumed that this may also have been present in the extract. The results of the study showed that lower body fat increased in the placebo group as the body mass index (BMI) of the subjects increased throughout the study. However, in the green tea extract group, the lower body fat decreased as the BMI increased throughout the study. Further in the placebo group, the % body fat increased with BMI throughout the study, but in the green tea extract group, the % body fat decreased as BMI increased throughout the study. Therefore green tea extract may have particular fat loss effects in overweight women although the pattern of fat loss may be complex and may involve fat reductions for particular body areas.
Eat Well, Stay Healthy, Protect Yourself
RdB
