Efficacy of a Green Tea Extract Rich in Catechin Polyphenols and Caffeine in Increasing 24-h Energy Expenditure and Fat Oxidation in Humans

Am J Clin Nutr. 1999 Dec;70(6):1040-5. doi: 10.1093/ajcn/70.6.1040.

Abstract

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 humans.

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.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipose Tissue / drug effects*
  • Adipose Tissue / metabolism
  • Adult
  • Caffeine / pharmacology*
  • Catechin / pharmacology*
  • Central Nervous System Stimulants / pharmacology*
  • Circadian Rhythm
  • Energy Metabolism / drug effects*
  • Humans
  • Lipid Metabolism
  • Male
  • Obesity / urine
  • Oxidation-Reduction
  • Plant Extracts / pharmacology
  • Tea*

Substances

  • Central Nervous System Stimulants
  • Plant Extracts
  • Tea
  • Caffeine
  • Catechin