Supplement analysis backed by scientific evidence · PT

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Limited evidenceWeight management

Green Tea Extract (EGCG)

Green tea extract is the single most common ingredient in "fat burner" formulas, and the Cochrane review found it produces essentially no weight loss — a pooled difference of 0.04 kg. Meanwhile, concentrated high-dose EGCG is one of the best-documented causes of supplement-induced liver injury.

What the science says

  • Causes weight loss Limited evidence

    The Cochrane review of RCTs lasting at least 12 weeks found a pooled mean difference of -0.04 kg in six studies conducted outside Japan, with BMI -0.2 kg/m² and waist circumference -0.2 cm, none statistically significant. Japanese trials were too heterogeneous to pool and ranged from no effect to -3.5 kg, typically using tea beverages containing caffeine rather than isolated EGCG. As a standalone fat burner, green tea extract does not work.

  • Enhances fat loss when combined with exercise Limited evidence

    A 2024 meta-analysis of 10 randomized trials comparing exercise plus green tea against exercise plus placebo in overweight and obese adults found small effects on weight (SMD -0.30), BMI (SMD -0.33) and fat mass (SMD -0.29), with no heterogeneity, and no additional benefit on lipid profile. The authors' own conclusion was that green tea offers "quite minimal" additive benefit over exercise alone.

  • Is safe because tea is safe Limited evidence

    Concentrated extracts are not tea. A toxicology review documented numerous published cases of acute hepatitis associated with green tea extract, including cases requiring transplant, with liver injury judged probable or highly probable by causality assessment. European regulators concluded that supplemental doses of 800 mg/day or more of EGCG are associated with raised liver transaminases; brewed tea carries no comparable signal.

Dosage & safety

Studied doseWeight-loss trials used roughly 100–800 mg/day of EGCG (often 270–1200 mg total catechins) for 12 weeks, usually alongside 80–300 mg of caffeine — the caffeine likely accounts for most of the acute thermogenic effect. The regulatory liver-safety threshold flagged for supplements is 800 mg/day EGCG. Brewed green tea at 2–3 cups supplies roughly 90–300 mg EGCG with no established hepatotoxicity signal.
SafetyHepatotoxicity is the headline risk: acute hepatitis, and rarely acute liver failure requiring transplant, reported with concentrated extracts. Risk is highest with high-dose catechin-enriched extracts taken on an empty stomach; a genetic susceptibility marker (an HLA-B variant) has been identified in a subset of cases. Take with food, avoid doses at or above 800 mg/day EGCG, and stop immediately for jaundice, dark urine, right-upper-quadrant pain or unexplained fatigue. Several jurisdictions including Health Canada and EU member states require liver warnings on these products. Other issues: green tea polyphenols markedly reduce non-heme iron absorption; catechins reduce plasma levels of the beta-blocker nadolol; and most fat-burner formulas add substantial caffeine on top. Avoid in pregnancy at supplemental doses (high catechin intake may interfere with folate metabolism).

Scientific references

Where to buy

NOW Foods, EGCg, Green Tea Extract, 400 mg, 180 Veg Capsules

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