In simplest terms, the more trans-fat you eat the more at risk you are for:
Medical researchers, the American Heart Association and government
agencies such as the FDA all agree that the American public needs to cut back
trans-fatty acids. Different from regular fats, trans-fats are created with
liquid oils are hydrogenated, or solidified, to lengthen food's shelf life
and change unsaturated "safe" fat into very harmful fat.
Trans fats raise levels of "bad" low-densty lipoprotein (LDL) cholesterol, triglycerides and insulin levels and reduce "good" high-density lipoprotein (HDL) cholesterol, which blocks important blood vessels potentially causing heart attacks. The leading culprit is margarine, which accounts for almost 25 percent of all consumed trans-fats. Contrary to popular belief, hydrogenated margarine is almost twice as harmful as natural butter. While the saturated fat in butter may raise the "bad" LDL, the trans-fat in margarine both raises LDL and depresses "good" HDL cholesterol, doing twice the harm.
People who are excessively overweight and obese do not reap the few benefits of substituting very low trans-fat margarine for butter, as most of the damage has already been done.
People who suffer from diabetes should especially steer clear of trans-fats, and they reduce the body's ability to handle blood sugar by lowering reponses to insulin.