Green Tea Extract (EGCG) for Weight Loss: Dosage and Safety

EGCG inhibits catechol-O-methyltransferase, the enzyme that degrades noradrenaline, which modestly prolongs adrenergic signalling and raises energy expenditure. The effect is amplified by caffeine, which is why the two are almost always formulated together and why trials of EGCG alone tend to read less impressively than the marketing.

• Energy expenditure: measurable increases in 24-hour energy expenditure in metabolic-ward studies, in the region of a few percent.
• Body weight: meta-analyses find reductions that are statistically significant and clinically small.
• Blood pressure and lipids: a meta-analysis in overweight and obese participants found improvements in blood pressure and lipid measures.
• Antioxidant status: consistently improved markers, with unclear translation to outcomes.

The United States Pharmacopeia published a comprehensive hepatotoxicity review of green tea extracts in 2020 and added a cautionary labelling statement. EFSA's scientific opinion on green tea catechins concluded that doses at or above 800 mg EGCG/day taken as a supplement have been shown to raise liver enzymes. The NIH LiverTox monograph is the standard clinical reference. The weight-loss literature is genuinely positive and genuinely modest.

Trials typically use 250-400 mg EGCG/day, usually alongside caffeine. Take it with food. This matters for safety rather than absorption: the case reports of liver injury cluster around fasted intake of concentrated extracts, and the European Food Safety Authority's review singled out that pattern.

Nausea, stomach upset and insomnia at higher doses, the last usually from the caffeine in combination products. The serious concern is hepatotoxicity: published adverse-event reports associate liver injury with EGCG intakes from roughly 140 mg to about 1,000 mg/day, with wide variation between individuals. Stop and seek medical advice for dark urine, jaundice, right-sided abdominal pain or unusual fatigue.

Reduces non-haem iron absorption, so it should be separated from iron supplements and iron-rich meals. Vitamin K content may affect warfarin control. Additive stimulant effects with caffeine from other sources. People taking a medication with its own liver burden should treat concentrated extracts with caution.