North Americans are about to get a better idea of just how unhealthy their diets may be. From potato chips to cookies and donuts, food makers will be revealing the amount of trans fat in their products.

The term may not mean much to most of us. But trans fats are one of the most dangerous kinds of fats, blamed for clogging arteries, raising cholesterol, and increasing the risk for heart disease.

Trans fats are hydrogenated fats -- oils that have been turned into solids by adding several hydrogen atoms to each molecule of oil. Hydrogenation makes the oil solid and less likely to become rancid. Because hydrogenation allows manufacturers to turn cheap, low-quality oils into feasible butter substitutes, hydrogenation is a thrifty method to add fat to processed foods.

Partially hydrogenated oils are in all kinds of processed foods, from solid or semi-solid margarines, to cookies, crackers, and cake mixes. They're also used for deep-frying donuts, fries and chicken.

But it's a form of fat that the body has trouble metabolizing. Some researchers believe that trans fat may be worse for heart health than saturated fat, because of the way it raises cholesterol levels.

Many consumers are not aware of the danger trans fat poses. So the U.S. is now forcing companies to come clean when trans fats are used in their products and label them. The new rules are similar to ones Canada introduced earlier this year.

The new Canadian and American guidelines are timely. The U.S. Chamber of Commerce anticipates hidden trans fats could spark a wave of lawsuits, such as the one an overweight American man launched against McDonald's. He alleged the food he ate at the restaurants every day made him fat.

The McDonald's case was thrown out of court. But the case was not unlike ones launched against tobacco companies, with plaintiffs charging that the manufacturers have acted negligently or deceptively in selling improperly labelled, dangerous products.

"The courts have been increasingly demanding that people have the right to know what the purveyor of products know, when that knowledge relates to risk or harm of those products," says Margaret Somerville, director of the Centre for Medicine, Ethics and Law at McGill University.

Because trans fats aren't labelled yet, Somerville believes a court could theoretically find a manufacturer negligent for not listing the content on the label.

So some food companies are being extra cautious. Kraft recently backed itself out of any potential lawsuits by announcing some major changes. The company announced that it's reducing portion sizes, reducing fat content, and ending advertising in schools. Frito-Lay has announced it's eliminating trans fat some of its snacks.

There's also pending legislation that would see the nutritional information posted beside every item on the menu board.

With a report from CTV's Jennifer Tryon

Tips for avoiding trans fats

1) Check the ingredient list on foods for the word ``hydrogenated.'' Eat foods with "partially hydrogenated vegetable oil" or "vegetable oil shortening" less often,

2) Buy a margarine that contains very little or no hydrogenated fat,

3) Use heart healthy oils more often - such as olive, canola, and flaxseed.