Green Tea Extract for Weight Loss
Green tea extract does not deliver clinically meaningful weight loss: across large meta-analyses any reduction is under 1 kg, the apparent benefit is mostly driven by added caffeine rather than catechins, and high doses carry a real risk of liver injury.
Why this grade7-layer evidence engine
The strongest evidence converges on a negligible effect, which is why this grades as counter-evidence. A 2012 Cochrane review of 1,945 adults (PMID 23235664) found no clinically important weight loss, with the six trials run outside Japan averaging just -0.04 kg (non-significant). A large 2024 GRADE-assessed meta-analysis of 3,802 participants (PMID 38031409) found only -0.64 kg of body mass at moderate certainty and a -0.16 kg/m2 BMI change at low certainty, with no effect on fat mass.
Where modest losses do appear, they are largely attributable to caffeine rather than catechins. A 2010 meta-analysis of 1,243 people (PMID 19906797) saw a -1.38 kg difference only when catechins were combined with caffeine, and no significant benefit for catechins alone. A 2009 meta-analysis (PMID 19597519) reported -1.31 kg but its own authors called the effect small and noted that habitual caffeine intake and ethnicity drive the response.
Regulators and clinics do not endorse it for weight loss. The FDA treats green tea extract only as a food antioxidant (GRAS), not a slimming aid, while the UK NHS/COT and other authorities flag dose-related liver toxicity above 800 mg/day of EGCG, and the WHO/IARC addresses only tea's carcinogenicity (Group 3), not weight. With Cleveland Clinic and Harvard Health both cautious, a sub-1 kg benefit does not justify the hepatotoxicity risk.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.428
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 negative 主導 (2 negative > 0 positive)，下層 RCT 不能推翻
- apply_hec_override — HEC-1 高階證據 negative — 強制由 C 改為 D
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status