Many restaurants and fast-food joints fry their french fries, fish, chicken and doughnuts in partially hydrogenated oils and shortenings, making these foods filled with trans fats. The FDA is considering a ban on partially hydrogenated oils, but they’re still rampant in processed foods. Unless you're in New York City, Philadelphia or California, where trans fats have been banned from restaurants, there's a good chance fried foods are a source of trans fat (exceptions include many major chains, which have switched to trans fat-free oils as trans fats have come under the lens of public scrutiny).