Green Tea and Metabolism: What the Science Really Says

When it comes to weight management, green tea often gets called a “metabolism booster.” But is that claim supported by science, or is it just hype?

A randomized clinical trial published in the American Journal of Clinical Nutrition looked into this question. Here’s what the researchers found — and what it means for you.

🔬 The Study at a Glance

• Who was studied? Healthy men were given either:
  
  

  • A green tea extract (rich in catechin polyphenols and caffeine)
    
    

  • Caffeine alone
    
    

  • A placebo
    
    

• What did they measure?
  
  

  • 24-hour energy expenditure (how many calories were burned in a day)
    
    

  • Respiratory Quotient (RQ), a measure of whether the body is burning more fat or carbohydrates for energy
    
    

📊 The Findings

• Participants taking the green tea extract burned about 4% more calories per day compared to placebo.
  
  

  • That translated to roughly 70–100 extra calories burned daily.
    
    

• Importantly, the effect was not seen with caffeine alone.
  
  

  • This suggests the benefit came from catechins — plant compounds naturally found in green tea — rather than caffeine.
    
    

• The green tea group also showed a lower RQ, meaning their bodies were burning a higher proportion of fat relative to carbohydrates.
  
  

⚖️ What This Means

• The study shows that green tea extract can have a modest effect on daily calorie burning and fat oxidation.
  
  

• This is not a miracle solution — but it does suggest green tea provides unique metabolic effects that are different from caffeine.
  
  

• This is an older study, but it measured metabolic rate specifically. More research is needed to confirm long-term impact, but this trial gives us a glimpse into why green tea continues to be studied for metabolism and weight management.

📚 Reference

Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J.
Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.
Am J Clin Nutr. 1999 Dec;70(6):1040–5. doi:10.1093/ajcn/70.6.1040. PMID: 10584049

🚀 Takeaway

Green tea extract isn’t a quick fix — but it does have science-backed, modest effects on metabolism and fat burning. For people looking to optimize their health, it can be one small piece of a bigger strategy that includes nutrition, activity, and personalized care.

👉 Want to learn how evidence-based strategies can support your health journey?
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