'If I had known that KFC uses an unnatural frying oil, and that their food was so high in trans fat, I would have reconsidered my choices,' said Dr. Arthur Hoyte, a retired physician.

Dr. Arthur Hoyte, a retired physician from Rockville, Md., and the Center for Science in the Public Interest, want a judge to order Kentucky Fried Chicken to use other types of cooking oils or make sure customers know about trans fat content immediately before they make a purchase.

KFC spokeswoman Laurie Schalow called the lawsuit frivolous and said the company will fight it in court. Schalow said KFC is looking at using other types of oil for cooking, but it is committed to maintaining "KFC's unique taste and flavor."

KFC provides nutrition and fat information to consumers online and in restaurants, Schalow said. "We have for a very long time," she said.

'Kentucky Fried Coronary'

Michael Jacobsen, the executive director of the Center for Science in the Public Interest, said Louisville-based KFC parent company Yum Brands Inc. knows that other, healthier cooking products are available.

"KFC knows this, yet it recklessly puts its customers at risk of a Kentucky Fried Coronary," Jacobsen said.

Hoyte said he is suing to force KFC to change its cooking practices "for my son and others' kids, so they may have a healthier, happier, trans-fat-free future."

"If I had known that KFC uses an unnatural frying oil, and that their food was so high in trans fat, I would have reconsidered my choices," Hoyte said.

Hoyte and the consumer group are seeking class-action status for the lawsuit and asking a judge to let Hoyte represent anyone who ate at a Washington, D.C.-area KFC in 2004 and 2005. Along with stopping KFC from using oil with trans fats, they are asking for a variety of economic damages.

Food Labels Required to List Trans Fats

The Food and Drug Administration says trans fat raises bad cholesterol. The government agency this year started requiring food labels to list trans fats.

The lawsuit is the second time in the last three years that KFC and the Center for Science in the Public Interest have crossed paths.

KFC settled a complaint filed by the group with the Federal Trade Commission in 2004 over ads claiming its fried chicken was compatible with then-popular low-carb diets.

Under the settlement, KFC also was barred from running advertisements saying that eating its food is healthier than eating another food unless it can back the claims up scientifically.