Green tea has been marketed as an herbal supplement for weight loss, however its potential benefits have been controversial. Green tea catechins (GTC), especially Epigallocatechin-3-gallate (EGCG), the most abundant catechins in green tea, are polyphenol compounds that have been the subject of a number of studies on the hypothesis that they may increase energy expenditure via thermogenesis effect, inhibit appetite, reduce nutrient absorption and increase fat oxidation.
The sympathetic nervous system (SNS) plays an important role in energy expenditure regulation and lipolysis. Its activities are influenced by the concentration of norepinephrine(NE) in the body. GTC inhibits the action of COMT enzyme which degrades NE, as so does caffeine, which is also present in green tea.
It is plausible that GTC and caffeine work synergistically in increasing energy expenditure shown in most acute and long term studies, while EGCG/GTC alone failed to elicit the same effect.
More favourable results on GTC’s effects on energy expenditure have been found in Asian population versus Caucasian, possibly due to genetic variability in enzyme activity.
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