Trans fat is a solid fat often manufactured from vegetable oils during a process called hydrogenation that raises unhealthy low-density lipoprotein cholesterol in your blood and increases your risk of heart disease, according to the U.S. Food and Drug Administration. The Dietary Guidelines for Americans 2010 suggest limiting trans fat in your diet as much as possible, and the American Heart Association recommends getting less than 1 percent of your total calorie intake from trans fat. This equates to less than 2 grams of trans fat daily when following a 2,000-calorie meal plan. Trans fat content is listed on nutrition facts labels of packaged foods.

Margarine

Hard stick margarine is generally made using hydrogenated vegetable oils. Therefore, they are often a source of trans fat and may contain up to 3 grams per tablespoon. To help reduce trans fat in your diet, replace hard stick margarine with vegetable oil when you cook. If you prefer the taste of butter, choose trans fat-free soft tub butter mixed with vegetable-oil, or trans fat-free soft tub margarine. While saturated fat found in butter may also raise bad cholesterol levels, PubMed Health suggests that saturated fat may not be as unhealthy as once thought -- and men can generally eat up to 30 grams daily, while most women can safely eat up to 20 grams of saturated fat per day.

Shortening

Because shortening is often a product of vegetable-oil hydrogenation, it too could be high in trans fat. However, some companies who manufacture shortening have altered recipe ingredients to significantly lower trans-fat content. Some shortening nutrition facts labels may state shortening is trans-fat free, but the American Heart Association notes that labels can claim products are free from trans fat if they contain less than 0.5 gram of trans fat per portion. If you see an ingredient listed on a food label that is "partially hydrogenated," it likely contains at least a small amount of trans fat.

Fast Foods

Many foods commonly sold at fast-food restaurant chains, such as doughnuts, French fries, fried chicken and burgers, are often sources of trans fat. While some fast-food restaurants have new trans fat-free recipes for some food products, trans fat has not been eliminated from all foods provided by fast-food chains. You can figure out how much trans fat is present in these food products by viewing nutrition facts information on company websites.

Baked Goods

Commercial baked goods and other snack foods -- such as biscuits, muffins, cinnamon rolls, ready-to-use frosting, crackers, cakes, pies and cookies -- are usually sources of trans fat. Many of these food items are also high in refined sugar and calories, but contain few essential nutrients like heart-healthy fats, fiber, protein, vitamins and minerals. Therefore, avoid commercial baked goods as much as possible to lower your disease risks and achieve or maintain a healthy body weight.

Pizza

Some pizzas, especially those with lots of pepperoni, sausage, bacon or beef on them, do contain some trans fat. Meat and dairy products, common ingredients on pizzas, provide small amounts of naturally-occurring trans fat, according to the American Heart Association. Check the nutrition facts labels of frozen pizzas to determine how much trans fat they contain. Keep in mind that if the amount if less than 0.5 grams of trans fat per serving, the label can claim the pizza is trans-fat free.