The agency isn't yet setting a timeline for the phase-out, but it will collect comments for two months before officials determine how long it will take. Different foods may have different timelines, depending how easy it is to find a substitute.
"We want to do it in a way that doesn't unduly disrupt markets," said Michael Taylor, FDA's deputy commissioner for foods. Still, he says, the food "industry has demonstrated that it is, by and large, feasible to do."
Though they have been removed from many items, the fats are still found in processed foods, including in some microwave popcorns and frozen pizzas, refrigerated doughs, cookies, biscuits and ready-to-use frostings. They are also sometimes used by restaurants that use the fats for frying. Many larger chains have phased them out, but smaller restaurants may still get food containing trans fats from suppliers.
Trans fats are widely considered the worst kind for your heart, even worse than saturated fats, which also can contribute to heart disease. Trans fats are used both in processed food and in restaurants, often to improve the texture, shelf life or flavor of foods. Diners shouldn't be able to detect a taste difference if trans fats are replaced by other fats.
To phase them out, the FDA said it had made a preliminary determination that trans fats no longer fall in the agency's "generally recognized as safe" category, which is reserved for thousands of additives that manufacturers can add to foods without FDA review. Once trans fats are off the list, anyone who wants to use them would have to petition the agency for a regulation allowing it, and that would likely not be approved.
The fats are created when hydrogen is added to vegetable oil to make it more solid, which is why they are often called partially hydrogenated oils. The FDA is not targeting small amounts of trans fats that occur naturally in some meat and dairy products, because they would be too difficult to remove and aren't considered a major public health threat on their own.
Scientists say there are no health benefits to trans fats and say they can raise levels of so-called "bad" cholesterol, increasing the risk of heart disease—the leading cause of death in the United States.
Many companies have already phased out trans fats, prompted by new nutrition labels introduced by FDA in 2006 that list trans fats and an by an increasing number of local laws that have banned them. In 2011, Wal Mart pledged to remove all artificial trans fats from the foods the company sells by 2016.
As a result of the local and federal efforts and many companies' willingness to remove them, consumers have slowly eaten fewer of the fats. According to the FDA, trans fat intake among American consumers declined from 4.6 grams per day in 2003 to around one gram per day in 2012.
Dr. Leon Bruner, chief scientist at the Grocery Manufacturers Association, said in a statement his group estimates that food manufacturers have voluntarily lowered the amount of trans fats in food products by 73%.
The group, which represents the country's largest food companies, did not speculate on a reasonable timeline or speak to how difficult the move may be for some manufacturers. Bruner said in a statement that "consumers can be confident that their food is safe, and we look forward to working with the FDA to better understand their concerns and how our industry can better serve consumers."
FDA officials say they have been working on trans fat issues for around 15 years—the first goal was to label them—and have been collecting data to justify a possible phase-out since just after President Barack Obama came into office in 2009.
The advocacy group Center for Science in the Public Interest first petitioned FDA to ban trans fats nine years ago. The group's director, Michael Jacobson, says the move is "one of the most important lifesaving actions the FDA could take."
He says the agency should try to move quickly as it determines a timeline.
"Six months or a year should be more than enough time, especially considering that companies have had a decade to figure out what to do," Jacobson said.