In 2006, on behalf of private plaintiffs, CSPI's Litigation Department filed a lawsuit against KFC based on its use of trans fat in its foods and failure to warn customers of the risks. Trans fat was finally banned by the FDA in 2015 because of its connection to coronary heart disease. However, in 2006, KFC’s Extra Crispy Combo contained 15 grams of trans fat. Shortly after the suit was filed, KFC agreed to cease its use of trans fat in cooking, and the suit was withdrawn.

Similarly, CSPI sued Burger King in 2007 about its use of trans fat. Although this suit was dismissed on procedural grounds, Burger King quickly agreed to halt its use of trans fat in cooking as well.