@Escoffier @TrevorGoodchild I have no evidence for this, but my intuition is that the process of making trans fats from oil is random by nature, and produces toxic byproducts. As to why those byproducts are bad.... trans fat specifically is way more rigid, stable and difficult to digest, while at the same time causing problems wherever it deposits. For example if it deposits in a cell membrane, it makes the membrane more rigid (like a heat shock protein) and less permeable. If this is the membrane of an arterial cell which has to be permeable in a specific way as well as contract/expand... it can cause a cell to break apart, which causes platelets to accumulate there, which leads to plaque.

At least thats my guess as to pathophysiology.