April 30, 2007/SAN FRANCISCO (MarketWatch) -- KFC said Monday it was stopped frying chicken in oil containing trans fat, while a sister brand, Taco Bell, said that all 5,600 of its U.S. restaurants have switched a cooking oil free of trans fat, according to company statements and media reports.

The announcements from the Yum Brands Inc. (YUM) units come during a national push to rid diets of trans fat, which doctors say can raise bad cholesterol and lower healthy cholesterol, Associated Press reported.

New York City and Philadelphia have ordered restaurants to phase out trans fat by 2008, and bills to restrict or ban trans fat in restaurants or school cafeterias have been introduced in a number of states, AP reported.

Louisville-based chain KFC said all 5,500 of its U.S. restaurants have stopped frying chicken in artery-clogging trans fat, AP reported, adding that the company had said in October that it was switching to a new soybean oil believed to be less likely to cause heart disease.

The chain will absorb the additional expense of the new cooking oil, which will not change the fried chicken's flavor, a KFC spokesman told AP.

Taco Bell said all 4,200 single-brand Taco Bells were converted to a canola oil, and all 1,400 multibrand locations switched to a soybean oil. Taco Bell said it's working to remove all trans fat from all its ingredients.

The company said it began the conversion from partially hydrogenated oil in November 2006 following more than two years of consumer testing.

The chains are subsidiaries of Louisville-based Yum Brands Inc., whose brands also include Pizza Hut, Long John Silver's and A&W All-American Food Restaurants.

Other companies including Wendy's International Inc. (WEN) , Starbucks Corp. (SBUX) , McDonald's Corp. (MCD) and Burger King Holdings Inc. (BKC) have also said they will phase out trans fat from their products, AP reported.

KFC was unveiling television advertising Monday to promote its switch to cooking oil without trans fat, according to reports, and stores will post advertising signs, while chicken containers will carry the message in a week or two, AP said.

From the May 9, 2007, Prepared Foods e-Flash