Take good old natural vegetable oils. Modify their molecular structure to create some abomination of nature and add it as an ingredient in pretty much everything that humans eat. the only benefit is that it create sa fat that has a shelf life measured in years rather than weeks.
Good old wikipedia has a nice article
http://en.wikipedia.org/wiki/Trans_fats
I like the quote "the NAS has concluded there is no safe level of trans fat consumption."