29 November 1999

Green with envy - the slimming properties of green tea

by Kate Melville

For sometime now there have been reports about the benefits of drinking green tea (as well as milk, wine, beer and most everything else). Anyway in addition to its potential to protect the heart, green tea extract may serve as an aid to weight loss! Clinical trials conducted by the University of Geneva, in Switzerland indicate that green tea appears to raise metabolic rates and speed up fat oxidation. Apparently in addition to caffeine, green tea contains catechin polyphenols that raise thermogenesis (the rate at which calories are being burned) and hence overall energy expenditure.

The study looked at ten relatively healthy young males who were obese (ranging from lean to mildly overweight). A typical Western non-weight-loss diet averaging 40% fat was prescribed during the course of research, and subjects were randomly assigned to each of three meals containing one of three treatments:

Green tea extract containing 50 mg of caffeine

50 mg capsule of caffeine by itself

A placebo

On three separate occasions each subject spent 24 hours in a specially designed respiratory chamber in which thermogenesis and energy expenditure were carefully measured. When gauged by these relatively sedentary circumstances the subjects' thermogenesis showed a 4% increase, and overall energy expenditure increased by 4.5%.

So far really only the impact of coffee has been studied in this area. But since caffeine also increase the heart rate, green tea appears seems to be a safer alternative for fat patients who may also have hypertension and or other cardiovascular problems. Of particular interest was that the subjects who received only caffeine, not green tea, showed no change in their metabolic rates. So the researchers have speculated that there is some sort of synergistic interaction between caffeine and other bioactive ingredients in green tea that helps promote a higher rate of fat burning.