EGCG has antioxidant, antibacterial, antidiabetic and hypocholesterolemic effects.
Thermogenic effects of EGCG have also been proposed, leading to its popular use as a weight-loss supplement.
In the Journal of Nutritional Biochemistry (2016), Kapoor and colleagues published a systematic review and meta-analysis to evaluate whether EGCG can indeed increase energy expenditure and promote fat oxidation in humans.
The meta-analysis included eight clinical trials. The trials were either crossover design or placebo-controlled, the dosages of EGCG ranged from 270–800mg per day, and the duration of the studies ranged from 2–12 weeks.
Outcome measures included energy expenditure (calories required during 24 hours at rest), respiratory quotient (ratio of carbon dioxide exhaled to oxygen inhaled), fat oxidation rate, body mass index, waist circumference and total body fat mass.
The pooled effects of EGCG supplementation on respiratory quotient and energy expenditure were statistically significant.
Compared with the placebo, the mean difference (MD) for respiratory quotient was -0.02 (95% CI, -0.04 to 0.0; p=0.01) and the MD for energy expenditure was 158kJ/d (95% CI, 4.72–311.38; p=0.04). No greater effect was seen for higher than lower dosages of EGCG. Effects on other outcome measures did not reach statistical significance.
The effect sizes reported in this meta-analysis were small, raising the question of their clinical relevance.
The authors conclude, nevertheless, that the reported effects on energy expenditure could reflect an increase in metabolic rate and improvement in fat oxidation.
They suggest that EGCG may be of mild benefit to metabolism when given at a dosage as low as 300mg per day.
