I was recently given a magazine article about a scientific study showing that oolong tea aids weight loss. Woo hoo! Of course, the scientist in me had to take a closer look…
The Good News: According to the article, rats prone to weight-gain were divided into two groups, and the ones that were given food laced with tea (dried extract of brewed tea) gained about 2/3 less weight than ones who had normal food, despite eating roughly the same amount. The “tea mice” who got 4% of their food intake as tea extract gained 20 grams, and those who got 2% of intake as tea gained 20 grams, while the “non-tea mice” gained roughly 120 grams each. The 2% dose in a human would be roughly 6 cups of strongly brewed tea per day. It’s thought that substances from tea leaves called saponins change how the body takes in fat, or the fats themselves, so the body doesn’t absorb as much.
The Bad News: First, a human drinking 6 cups of strong tea may well be different than a rat eating extract of brewed tea. While I’d love to use this study as an excuse to recommend anyone over average weight to drink six cups of tea a day, I’d like to see some kind of human study, or one showing that the action of tea saponins works the same way chemically in a human gut as it does in a rat gut.
Second, although I found more information about the study from the magazine’s website including the title (“Oolong tea reduces food intake, body weight, and body fat in spontaneously obese rats”), I couldn’t find any references to the study outside of the magazine’s site and a couple of blog posts in an admittedly fairly quick search. Apparently, the study was reported at the Experimental Biology ’07 meeting, and may not have been actually published. I did a search for the authors and didn’t find anything about the primary author, and a CV of an “et al” author that didn’t list this study under her “selected publications.”
Of course, this doesn’t mean the study doesn’t exist, but it makes it hard to evaluate the study if you can’t find the study that you’d like to evaluate. However, it is interesting in that it offers data connecting tea with weight loss as well as the mechanism by which it might work. (Previous to reading the article, I had always assumed that any weight loss from tea drinkers versus non-tea-drinkers was probably due to caffeine speeding up the body a bit and thus burning a bit more energy.)