They also are sometimes used by restaurants for frying. Many larger chains have phased them out, but smaller restaurants may still get food containing trans fats from suppliers.
How can the government get rid of them? The FDA said it has made a preliminary determination that trans fats no longer fall in the agency's "generally recognized as safe" category, which covers 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.
Many companies have already phased out trans fats, prompted by new nutrition labels introduced by FDA in 2006 that list trans fats and by an increasing number of local laws, like one in New York City, that have banned them. In 2011, Wal-Mart pledged to remove all artificial trans fats from the foods the company sells by 2016. Recent school lunch guidelines prevent them from being served in cafeterias.
In a statement, New York City Mayor Michael Bloomberg said it was his city's 2008 ban that led to much of the progress. "Our prohibition on trans fats was one of many bold public health measures that faced fierce initial criticism, only to gain widespread acceptance and support," he said.
Indeed, consumers are eating less of the fat. According to the FDA, trans fat intake among Americans declined from 4.6 grams per day in 2003 to around one gram in 2012.