Where you find them: Hiding in many of the fried and baked foods we love, including French fries, doughnuts, cookies, pastries, crackers and microwave popcorn, as well as stick margarine and shortening.

How to spot them: Solid at room temperature.

Why they're bad: They raise your ''bad'' LDL cholesterol levels. They may also lower your high-density lipoprotein (HDL) or ''good'' cholesterol levels, increasing your risk of heart disease, stroke and type 2 diabetes.

AHA recommends: Limit consumption of trans fats to less than 1 percent of your total daily calories. Watch out though—foods labeled ''trans fat-free'' may be high in saturated fats (and low in nutrients and fiber). Swap the bag of chips for some nutrient-rich snacks like cut vegetables or fruit, or unsalted mixed nuts.

NEXT: More monounsaturated fats>>