First, some good news: manufacturers have significantly reduced the amount of trans fats in packaged foods. Even better, according to a 2012 Centers for Disease Control study of white American adults, blood levels of trans fats dropped by a whopping 58 percent between 2000 and 2009. "This decline shows substantial progress that should help lower the risk of cardiovascular disease in adults," says Christopher Portier, Ph.D., director of the CDC's National Center for Environmental Health.

Why? Trans fats raise your "bad" LDL cholesterol, possibly even more than saturated fats do. Trans fat also lowers your "good" HDL cholesterol. The American Heart Association recommends limiting the amount of trans fat to less than 1 percent of your total daily calories. If you eat 2,000 calories a day, that translates to about 2 (or fewer) grams.

Bottom Line: Trans fats may still be lurking in packaged snacks, crackers, bakery goods and some margarines. (Trans fats are also found naturally-albeit­ in small amounts-in beef, pork, lamb and butterfat.) A package can claim a food has "zero trans fat," if the amount per serving is less than 0.5 g. To make sure a product is trans-fat-free, check the ingredient list: if "hydrogenated oil" or "partially hydrogenated oil" are listed, the product contains trans fat.