Trans fats became popular because of their versatility in food production. They make processed foods "shelf-stable," able to stay on supermarket shelves for months without going bad. Fast food restaurants loved trans fats because they could be used repeatedly in commercial deep fryers without having to be replaced, according to the American Heart Association.
But, trans fats gained a notorious reputation because they literally do everything wrong in the human body when it comes to cholesterol.
They also cause inflammation, said Penny Kris-Etherton, a registered dietitian and professor of nutrition at Penn State University. "Inflammation is not only a root cause of heart disease, but other chronic diseases as well," she said.
Trans fats, which are man-made, shouldn't be confused saturated fats or unsaturated fats.
Saturated fats are considered "bad" fats because they increase your "bad" cholesterol levels, which can cause artery-blocking plaques. Unsaturated fats are considered "good" fats because they increase your levels of "good" cholesterol, a type of cholesterol that actually helps carry away the "bad" cholesterol and prevent plaques.
The use of trans fats has decreased as public knowledge of their health risks increased. New York City banned trans fats in restaurants in 2006. And studies have found that fast-food chains like McDonald's, Burger King and Wendy's have significantly decreased the amount of trans fats used in their french fries.
Food manufacturers also have been limiting the use of trans fats, most notably since the FDA required in 2006 that trans fats be listed on the Nutrition Facts labels placed on nearly all food products.
"As a result of that decision, we have greatly reduced trans fats in the food supply," said Kris-Etherton. "Consumers have become more health- conscious and that has not worked well for the trans fats industry."
The move away from trans fats already has been reflected in the diet of the average American. Trans fat intake has declined per person from 4.6 grams per day in 2006 to about one gram a day in 2012. Levels of trans fatty acids in the blood of white adults in the United States declined 58 percent between 2000 and 2009, according to the U.S. Centers for Disease Control and Prevention.