Yum Brands, operator of KFC, is facing a class-action lawsuit over the chicken fast-food chain’s use of artery-clogging trans fat for frying foods.

The Center for Science in the Public Interest, a non-profit food and nutrition lobby group, on Tuesday filed suit against Yum Brands in the Superior Court for the District of Columbia, alleging KFC “does not properly warn, disclose, or even tell its customers that they are eating food items prepared with the worst oil available and imaginable”.