December 4, 2023

Is Green Tea Really the Miracle Weight Loss Potion It’s Made Out to Be?

Author: Kate Findley
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By Michael Ormsbee, PhDFlorida State University
Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

In addition to coffee, another supplement with a potential fat loss effect is green tea. Both green tea and green tea extracts have become increasingly popular in American culture over the past decade. Professor Ormsbee investigates the research on its fat-burning effects.

Pouring green tea into a cup
Just like coffee, green tea has been found to assist in weight loss due to its fat-burning effects; however, the amount needed would be equivalent to 15 cups per day. Photo By kai keisuke / Shutterstock

Green Tea and Weight Loss

Before being used as a weight loss supplement, green tea has been used in Eastern cultures for much longer to increase mental awareness, improve digestion, and regulate body temperature, in addition to acting as an antioxidant and for its anti-obesity and anti-cancer effects. The active ingredient in green tea is called epigallocatechin gallate, commonly known as EGCG.

Essentially, EGCG is thought to block an enzyme called catechol-O-methyltransferase, or COMT that prevents norepinephrine from being degraded and prolongs norepinephrine’s thermic action in your body. Norepinephrine’s thermogenic effect consists of helping to release fat from fat cells and to increase energy expenditure.

In some studies, EGCG has been shown to increase energy expenditure by about four percent and increase fat burning by roughly 10% compared to a placebo. Interestingly, when combined with caffeine, which also preserves norepinephrine’s thermogenic action, there seems to be a synergistic effect between caffeine and EGCG, which in some studies has been shown to ramp up fat burning more than caffeine or EGCG alone.

Importance of Supplementation

“But, I wouldn’t run off to the supermarket and start buying everything with green tea just yet,” Professor Ormsbee said.

In order to have a beneficial effect, the research shows that you need to consume about 750 mg per day of EGCG. This is a huge dose. 

One cup of green tea only has about 50 mg of EGCG, which means you would need to drink about 15 cups of green tea per day. However, you don’t have to turn green drinking all your EGCG. 

Many EGCG supplements are found in capsulated form with about 400 mg per pill. Thus, taking two per day would achieve the required amount shown to be effective in research studies. Remember to check with your health care professional about taking any supplements.

Many teas and supplements contain both EGCG and caffeine. Even drinking decaffeinated green tea may improve body composition. 

A recent study found that consuming a decaffeinated green tea extract of 571 mg of EGCG per day for four weeks, resulted in a nearly two percent decrease in body fat and a 25% increase in fat oxidation during moderate-intensity exercise. Interestingly, the decaf green tea also improved exercise performance in these young men.

Other Fat Loss Supplements

While caffeine and EGCG in tea are two of the main fat loss supplements on the market, others are easily accessible and have some evidence to back them up. Capsaicin is a spice that causes the perceived hotness that you feel when eating spicy foods. This pungent extract has been shown to increase thermogenesis and energy expenditure by enhancing—you guessed it—norepinephrine release.

The issue is that many of these studies have used rats and not humans as research subjects. Thus, you have to be cautious about generalizing these results to humans. 

The data for humans is less impressive. Body fat reductions have been reported—the issue is that there is a high rate of weight regain, and the participants had trouble sticking to the dosage that is thought to be required for a beneficial effect.

Another debatable supplement for fat loss is called carnitine. Carnitine is a fat carrier or gatekeeper that helps transfer fat into the mitochondria where it gets oxidized for fuel. 

Logically, it makes sense that if you increase the amount of carnitine, then you could get more fat into the right place to burn it for energy. Unfortunately, that is not the case in 99% of the research on this topic. 

Until more long-term studies are completed, it doesn’t appear to be worth it. Numerous other supplements exist like conjugated linoleic acid or CLA, chitosan, yohimbine, and others. However, according to Professor Ormsbee, research trials with humans do not provide enough evidence to show any consistent fat loss effect from these supplements.

Best Way to Lose Weight

Therefore, only a few fat loss supplements have real evidence to support their use. Time and time again, the beneficial effect from these supplements comes when combined with exercise training. 

Even for the products that have demonstrated the ability to increase thermogenesis and overall calorie burn, it is usually quite small. Thus, if you bank on a supplement to help you lose weight or fat without considering your overall nutrition and exercise habits, you are in for a long, expensive, and unsuccessful battle with body composition. 

In fact, many people feel that when they take fat loss supplements, they can loosen up their good eating patterns because the pill will do the work for them. This couldn’t be any further from the truth. 

“In fact, we published research on an ineffective weight loss pill that contained caffeine, green tea, CLA and some amino acids,” Professor Ormsbee said. “Turns out that eight weeks of taking the pill, but not exercising resulted in no changes in body composition at all.”

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.
Dr. Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University.

Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his MS in Exercise Physiology from South Dakota State University and his PhD in Bioenergetics from East Carolina University.

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