Green Tea & Metabolism

Does green tea boost metabolism?

Yes, modestly. Green tea catechins (especially EGCG) combined with caffeine increased 24-hour energy expenditure by ~4% in a landmark 1999 trial (PMID 17201629). 2009 meta-analysis confirmed effect on weight loss/maintenance.

What is EGCG?

Epigallocatechin gallate - the most abundant catechin in green tea and most-studied for metabolism. A polyphenol antioxidant that inhibits the enzyme breaking down norepinephrine, prolonging its fat-oxidation effects.

Why does green tea need caffeine?

Catechins and caffeine are synergistic. Studies isolating EGCG without caffeine show weaker effects. Green tea naturally contains both.

Catechins and Their Role

Tea contains catechins (EGCG, EGC, ECG, EC). EGCG is the most concentrated and most-studied. Powerful antioxidants - but for fat loss, the key effect is on catecholamine signaling.

The Norepinephrine Connection

Norepinephrine triggers fat cells to release stored fatty acids. The enzyme COMT breaks down norepinephrine. EGCG inhibits COMT, prolonging norepinephrine's active life. The 1999 Dulloo paper (PMID 17201629) demonstrated this with calorimetry.

The Meta-Analytic Evidence

Hursel et al. (2009) pooled 11 RCTs in Int J Obesity (PMID 19597519) - catechin-rich teas with caffeine produced modest but statistically significant effects on weight loss and maintenance.

How Much Do You Need?

Effective doses in trials: 200-400 mg catechins (100-200 mg EGCG) plus 50-100 mg caffeine daily. A cup of green tea has ~50-100 mg catechins, so clinical-trial doses from tea alone require 4-6+ cups. Concentrated extracts (like the green tea in Metabo Drops) deliver these doses in smaller volume.

Safety

Generally well-tolerated. Very high doses (above 800 mg EGCG daily on empty stomach) have been associated with rare liver toxicity. Standard supplement doses are well below this threshold. Anyone with liver disease should consult a doctor.