“That will make it a challenge, to be honest,” said Michael R. Taylor, deputy commissioner for foods at the F.D.A.  Dr. Margaret A. Hamburg, the agency’s commissioner, said the rules could prevent 20,000 heart attacks and 7,000 deaths from heart disease each year.

The move concluded three decades of battles by public health advocates against artificial trans fats, which occur when liquid oil is treated with hydrogen gas and made solid. The long-lasting fats became popular in frying and baking and in household items like margarine, and were cheaper than animal fat, like butter.

For the FDA press release, go to FDA press release