Slimming on oolong.

Without skimping on portions, rats eating diets including oolong tea gain less weight than those dining teafree, a new study finds. The tea apparently impairs the body's ability to absorb fat.

The finding supports a weight-control strategy--oolong consumption--advocated by practitioners of traditional Chinese medicine, note Lauren E. Budd and her colleagues at the University of California, Davis.

The researchers worked with a strain of adult female rats that spontaneously become obese on a normal diet. For 10 weeks, the team let the animals eat all they wanted but laced the chow of some with a dried extract of brewed tea. Although all the animals ate about the same amount, Budd says, those getting 2 and 4 percent of their food as tea extract by weight gained only about 40 and 20 grams, respectively, over the period. Rats consuming unsupplemented chow packed on roughly 120 grams each.

The 2 percent dose corresponds to the amount of solids in about six cups of strongly brewed tea per day, Budd says.

Blood concentrations of triglycerides--fats--were about 80 percent lower in the tea-treated rats than in those eating unsupplemented chow, Budd reported on May 1 in Washington, D.C., at the Experimental Biology '07 meeting. Tea-treated animals also accumulated just 12 to 20 percent body fat, versus about 35 percent in animals eating unsupplemented chow.

Saponins, waxy substances from the tea leaves, after how the body processed some fat, which then moved through the gut without being absorbed, says Budd's colleague Judith S. Stem.--J.R.