A U.S. consumer group sued the operator of the KFC fried chicken restaurant chain on Tuesday to try and force it to stop it from frying foods in an artery-clogging fat.

The Center for Science in the Public Interest, in a suit filed against Yum Brands Inc. (YUM) in the Superior Court for the District of Columbia, said some KFC meals were "startlingly" high in artery-clogging trans fat from the partially hydrogenated oils used for frying.

CSPI Executive Director Michael Jacobson said it was harder to avoid trans fat at KFC than at other fast-food restaurants.

"Trans fat is almost everywhere on this menu. By frying in such a dangerous oil, KFC is making its unsuspecting consumers' arteries Extra Crispy," he said, referring to a version of fried chicken sold by KFC.

The suit seeks to force the KFC chain to stop cooking with trans fat or prominently warn customers about the health hazard.

KFC "does not properly warn, disclose or even tell consumers that they are eating food items prepared with the worst oil available," the group said in a legal complaint.

The group asked the court to switch to a healthier frying oil. If that is ruled out, the group asked the court to require signs at KFC outlets saying "KFC fried chicken and certain other foods contain trans fat, which promotes heart disease."

A KFC spokeswoman was not immediately available for comment.

CSPI said a typical three-piece combo meal with an Extra Crispy chicken drumstick, two Extra Crispy thighs, potato wedges and a biscuit contained 15 grams of trans fat.

Health experts suggest minimizing trans fat consumption as much as possible. Research shows it raises LDL or "bad" cholesterol while lowering HDL, the "good" cholesterol.

Last week, No. 3 U.S. burger chain Wendy's International Inc. (WEN) said it would significantly cut trans fat from its menu by switching to a new blend of corn and soy oil for french fries and breaded chicken items. McDonald's Corp. (MCD) vowed in 2002 to remove trans fat from its french fries in the United States but has not done so.

Yum Brands, based in Louisville, Kentucky, also operates the Pizza Hut and Taco Bell fast-food chains.