Normal fatty acids have a natural curve to their molecular shape. When they fit together in vast numbers, enough space still remains so that the cell membrane has the proper structure it needs to function at its best.
However, if these same fat molecules are changed by manufactured food processes, or if they are heated for long periods – as in deep frying – they mutate into a form rarely found in nature. Now their molecules are straighter, narrower, and no longer have their original curved shape.
This means that these altered fats will pack more tightly together into the cell membrane, making it more saturated and rigid – less flexible and less able to function properly. These altered fats are called "trans fatty acids," and are finally being recognised for the damage they cause...They will kill you!