January 6, 2009

You Ask, I Answer: Green Tea & Weight Loss

Do you think all the hoopla about drinking green tea has merit for weight loss?

-- Beth (last name withheld)
Portland, ME

This is one of those situations where the science certainly looks promising, but when I consider what we currently know about human application, I think people are jumping the gun.

There is yet to be any major study showing how green tea affects human weight loss.

For example, a well-known 1999 human study published in the American Journal of Clinical Nutrition which concluded that flavonoids present in green tea (known as cacethins) had metabolism-boosting properties only consisted of ten subjects.

The most extensive studies on this topic have been done on mice.

One of the latest studies, published in the February 2008 issue of the Journal of Nutrition, focused on mice with a genetic predisposal to obesity.

That study, like several others, showed what appears to be a strong link between a polyphenol in green tea known as EGCG (that stands for epigallocatechin-3-gallate, in case you were wondering) and weight.

More specifically, the mice on a diet supplemented with EGCG gained less weight than those whose diet did not contain the extract.

It is worth pointing out that in that particular study, the mice on the EGCG diet consumed the human equivalent of seven cups of green tea.

Which leads me to why I find blanket statements like "green tea burns fat" to be overly simplistic.

First of all, it appears that to experience any of the thermogenic (body temperature raising) effects, humans need to drink at least seven cups a day.

Second, from the limited studies on humans, it appears that these components in green tea raise calorie expenditure through thermogenesis (essentially heat production) by approximately 4 percent.

Now it's time for some math.

Let's assume that within a 24 hour period of complete rest (think doing nothing but laying on a bed -- this is known as your basal metabolic rate) your body burns 1,500 calories.

If you apply the four percent increase from that particular human study, you can conclude that consuming
seven cups of green tea a day would raise that total to 1,560 calories.

Keep in mind, though, that if you sweeten each of those seven cups of tea with just one teaspoon of sugar, you are tacking on 112 calories to your day.

So, here is my stance. If you enjoy sipping green tea, that's great.

It's a wonderful beverage that, when consumed plain, offers not only a variety of polyphenols and antioxidants, but also an absence of calories.

However, as regular readers of this blog know, I oppose the attribution of weight-loss characteristics to specific foods, as it is ultimately overall eating patterns -- and caloric intake -- that affect weight.

So, if green tea is not to your liking, you are not at a weight-loss disadvantage.

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