Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans by Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J.
BACKGROUND: Current interest in the role of functional foods in
weight control has focused on plant ingredients capable of
interfering with the sympathoadrenal system.
OBJECTIVE: We investigated whether a green tea extract, by
virtue of its high content of caffeine and catechin polyphenols,
could increase 24-h energy expenditure (EE) and fat oxidation in
DESIGN: Twenty-four-hour EE, the respiratory quotient
(RQ), and the urinary excretion of nitrogen and catecholamines were
measured in a respiratory chamber in 10 healthy men. On 3 separate
occasions, subjects were randomly assigned among 3 treatments:
green tea extract (50 mg caffeine and 90 mg epigallocatechin
gallate), caffeine (50 mg), and placebo, which they ingested at
breakfast, lunch, and dinner.
RESULTS: Relative to placebo, treatment with the green tea
extract resulted in a significant increase in 24-h EE (4%; P <
0.01) and a significant decrease in 24-h RQ (from 0.88 to 0.85; P
< 0.001) without any change in urinary nitrogen.
Twenty-four-hour urinary norepinephrine excretion was higher during
treatment with the green tea extract than with the placebo (40%, P
< 0.05). Treatment with caffeine in amounts equivalent to those
found in the green tea extract had no effect on EE and RQ nor on
urinary nitrogen or catecholamines.
CONCLUSIONS: Green tea has thermogenic properties and promotes
fat oxidation beyond that explained by its caffeine content per se.
The green tea extract may play a role in the control of body
composition via sympathetic activation of thermogenesis, fat
oxidation, or both.
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