Healthcare providers consider trans-fat to be the worst type of fat you can eat, say researchers at the Mayo Clinic.

Unlike other dietary fats, trans-fat, also called trans fatty acids, raises your low-density lipoprotein, or LDL, which is considered to be the harmful type of cholesterol, and lowers high-density lipoprotein, or HDL, considered to be beneficial.

A diet laden with trans-fat increases your risk of heart disease, the leading killer of American men and women.

Some foods, like meat and dairy products, contain naturally occurring trans-fats. But when certain foods are prepared with hydrogen added to vegetable oil—called hydrogenated oil—they become potentially lethal weapons.

Adding hydrogen to oil helps keep it stable at room temperature. By wreaking havoc with your cholesterol levels, these oils may leave fatty deposits on your arteries which can rupture and tear, potentially forming a blood clot what may cause a heart attack or stroke.

Foods most likely to have trans-fat:

• Baked goods. Most cookies, cakes, pies and crackers are baked with shortening which is usually made with partially hydrogenated oil. Readymade frosting is another common source of trans-fat.
• Snacks. Potato, corn and tortilla chips often contain trans-fat. Homemade popcorn is a healthy snack when its air-popped but many types of packaged and microwave popcorn have unhealthy levels of trans-fat.
• Fried food. Foods that require deep frying such as french fries, doughnuts and fried chicken can contain trans-fat from the cooking process.
• Refrigerated dough. Products such as canned biscuits and cinnamon rolls often cotain tranfat, as do frozen pizza crusts.
• Creamer and margarine. Non-dairy creamer and stick margarines many also be trans-fat villains.

Check labels for trans-fat listing as well as information about partially hydrogenated oil on the ingredient list. This indicates that the food contains some trans-fat even if the label does not list trans-fat specifically.

The U.S. Food and Drug Administration (FDA) has determined that hydrogenated vegetable oil is no longer “generally recognized as safe” and should be phased out of production over the next several years.

The Mayo Clinic strongly advises everyone to steer clear of trans-fats and also products that contain coconut, palm kernel and palm oils—which all contain lots of saturated fat.

In a healthy diet, 20 percent to 30 percent of your total daily calories can come from fat—but saturated fat should account for less than 10 percent of this total.

"Stick to monounsaturated fat which is found in olive, peanut and canola oils,” say researchers. “Nuts, fish and other foods containing unsaturated omega-3 fatty acids are other good choices of foods with healthy fat."