A plaintiff’s class certification effort in a false advertising suit against the makers of an allegedly trans-fat-free product was derailed Monday, after the district court found concerns her unique defenses would become the focus of the litigation.

Suzanna Bowling filed suit against McNeil Nutritionals and its parent company Johnson & Johnson over their butter alternative Benecol, which is advertised as having no trans fat. Bowling, who claims to have a severe sensitivity to trans fats, stated that she purchased a tub of Benecol Light from a Walmart in White Plains in mid-2011.