Contents

Page 1
Green tea and thermogenesis
How powerful is green tea thermogenesis?
Energy expenditure.
Respiratory quotient.
Page 2
Noradrenaline storage & release.
Noradrenaline metabolism.
How green tea stimulates thermogenesis.
Discussion.
Page 3
Green tea products.
Green tea for weight loss.

The color (green, oolong, and black) of tea (Camellia sinensis) is determined by how it is manufactured. Green tea is prepared in such a way as to avoid the oxidation of the polyphenols; oolong tea is partially oxidized; black tea is largely oxidized.

The composition of tea is determined by soil conditions, the season the leaves are harvested, and the method used to process the tea. As a rough guide, green tea contains 2.9 to 4.2% caffeine, 0.02 to 0.04% theophylline, and 0.15 to 0.2% theobromine. Green tea also contains theanine, an important water-soluble amino acid that is converted to catechin by sun light. The greatest theanine content is found in the highest grade green tea, Gyokuro, which is cultivated without direct sunlight.

Green tea also contains a number of polyphenolic compounds. The catechin epigallocatechin gallate (EGCG) is the most abundant (> 50% of total tea catechins). It is also believed to be the most pharmacologically active. The other main catechins are epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin (EGC). You can view the chemical structures in a new window.

In addition to stimulating thermogenesis, green tea has a variety of well documented health benefits. Green tea is an antioxidant that has a strong anticancer effects in skin, stomach, colon, etc. Green tea protects against free radicals and it is a logical addition to any supplement program designed to prevent heart disease. In fact, green tea has so many health benefits that this post will have to focus on its ability to stimulate thermogenesis.

Quick facts: The Dulloo et al. studies (1, 2) used an alcohol extract of green tea that is sold in capsule form under the name EXOLISE (Arkopharma Laboratories, Nice, France). This extract is standardized to 24.7% catechins (70% as EGCG), and 8.35% caffeine.

How Powerful Is Green Tea Thermogenesis?

Scientists have found that green tea stimulates thermogenesis and this effect cannot be completely attributed to its caffeine content because the thermogenic effect of green tea is greater than an equivalent amount of caffeine. An in vitro study by Dulloo et al (2) found that a catechin that is abundant in green tea, EGCG, increased the respiration rate of brown fat (stimulated thermogenesis). Dulloo et al. have also done an in vivo study (1) that involved "10 healthy men" who received (with each meal during a 24 hour test period) on three separate occasions:

Test 1: 50 mg caffeine and 90 mg EGCG (total catechins: 125 mg).

Test 2: 50 mg caffeine.

Test 3: Placebo.

There was a "5-10 day interval between successive 24-h trials for each subject." The conditions were controlled and the study was double blind. However, given the fact that obese people respond differently to sympathetic  stimuli, it is unfortunate that these tests were performed on "healthy" subjects. The study accepted people described as ranging from "lean to mildly obese" (8-30% bodyfat). But the responses varied widely nonetheless: 24 hour energy expenditure increased "in 6 of the 10 subjects after treatment with the green tea extract, ranging from 266 to 836 kJ" They did not find a correlation between the magnitude of thermogenic response and the degree of fatness of the subjects. That's not too surprising given the number of subjects and the selection criteria. It's a shame that they didn't include more subjects and some fat people in these tests.

Energy Expenditure

Diurnal and 24 hour energy expenditure was increased significantly during treatment with green tea extract. Nocturnal energy expenditure increased, but not significantly. Here's the numbers:

• Diurnal: Green tea 4.5% > placebo; Green tea 3.2% > caffeine.
• 24 hour: Green tea 3.5 % > placebo; Green tea 2.8 % > caffeine.

Perhaps even more interesting is the fact that the green tea extract produced lower respiratory quotients (helped normalize FAT burning):

"Significant differences across treatments were found during the diurnal, nocturnal, and 24-h periods . . . The contribution of fat oxidation [fat burning] to 24-h EE [energy expenditure] during treatment with the green tea extract (41.5%) was significantly higher (p<0.001) than during placebo [31.6%] treatment" (1).

In addition, urinary nitrogen losses showed no significant differences across treatments during all three periods. Clearly, the increased energy expenditure reflects increased FAT burning. This is worth exploring in greater detail.

Written
Dec 2000
Last Update
Dec 2000

Respiratory Quotient

Now we are getting to the interesting stuff. The lower the respiratory quotient, the more fat you are burning. You will often see this referred to as substrate utilization, substrate oxidation (burning), or fuel mix. It is very encouraging that such a small dose of green tea had such an impressive effect on the RQ: The contribution of fat oxidation [fat burning] to 24-h EE [energy expenditure] during treatment with the green tea extract (41.5%) was significantly higher (p<0.001) than during placebo [31.6%] treatment" [emphasis added] (1). Outside of medical journals, fat oxidation and the respiratory quotient are usually only discussed in relation to aerobic exercise (I'm sure you have been told to do low intensity aerobics to burn more fat). However, as usual, the interesting stuff (the stuff that proves obesity is a REAL disease) is ignored.

You see, obese people tend to burn more carbohydrate (glucose) and less fat (fatty acids) than normal people. The Astrup/Toubro team of obesity researchers have studied this defect (4-NA, 5-NA). In fact, a growing number of scientists believe that this part of the thermogenic defect may be more important than energy expenditure. Why do we burn relatively less fat? This is caused be a number of genetic (22) and biochemical defects including insufficient release of noradrenaline and adrenaline. Arne Astrup et al. (5-NA, 22) have written about this genetic defect:

"Direct evidence for a genetic influence on RQ [respiratory quotient] was delivered by Deriaz et al., who studied the relationship between DNA variation at the genes coding for the Na,K-ATPase peptides, RQ, and body fat. Postabsorptive [after a meal] RQ was found to be associated with the alpha2-gene and linked with the beta-gene of the Na,K-ATPase, which suggests that these, or neighboring genes, influence RQ. Twin studies also support the heritability of RQ." [emphasis added] (5-NA).

Based on this study by Dulloo et al. (1), it looks like green tea can help correct this respiratory quotient defect. Of course, ephedrine/caffeine normalizes the release of noradrenaline and adrenaline and corrects the respiratory quotient:

"The respiratory quotient (RQ) indicate that relatively more lipid [fat] was oxidized during chronic ephedrine treatment than in the control study. This change was observed in the fasting state as well as after glucose administration. Certain effects of ephedrine seems to be appropriate to a thermogenic drug for the treatment of obesity: A single dose of ephedrine stimulates thermogenesis, an effect that is enhanced during chronic treatment; Chronic treatment elevates the metabolic rate; and the substrate utilization is changed in favor of lipid [fat] oxidation" [emphasis added] (6).

Is it not curious that doctors tell obese people to eat an abnormally small amount of fat rather than tell us to take thermogenic supplements to correct this genetic fat burning defect? I mean, imagine if your car was having engine trouble and your mechanic refused to fix it and told you to "just drive less." Of course, you would immediately realize that this was a bogus 'solution' and go to another mechanic. But what if they ALL ignored the problem and told you to change your driving habits? Eventually you would realize that you need to read some repair manuals so you can fix the car yourself, right? Fortunately, there is no FDA-type organization trying to pass laws against nonprofessional car repairs.

Obese people who do not want to be mislead by prejudice, ignorance, or political/financial agendas should keep this fuel mix defect in mind when they hear "experts" questioning the importance of thermogenesis. Typically, these "experts" will rattle off a bunch of energy expenditure numbers and tell you that thermogenesis is not very important and thermogenic supplements don't do much. If you want to have some fun, remind the "expert" that there is direct evidence for a genetic influence on respiratory quotient and one of the ways that thermogenic supplements help obese people is by normalizing their defective substrate utilization. Ask the "expert" if he is aware of the fact that a growing number of obesity scientists believe correcting this genetic fat burning defect is more important than those archaic energy expenditure numbers. After all, if you don't BURN fat, you BECOME fat.

   
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