Why are trans fats worse than saturated fats?
Someone may very well give a more thorough answer but from what I understand, most naturally occurring unsaturated fats have their double bonds in the cis conformation which is generally higher in energy than the trans conformation.

Thus, the idea is that when you ingest trans fats (i.e. fats with a trans double bond) your body has to somehow hydrogenate this double bond before it can break it down further. This is more difficult for your body to do because it must either isomerize to a cis bond and then hydrogenate, or just hydrogenate the trans bond which is not easy for your body to do effectively. In some cases hydrogenation of trans fats can't actually happen because nature basically makes cis double bonds in fats (which sounds weird but is true) so your body has ways of breaking these fats down but not trans fats. So, the fat just gets stored or excreted without doing anything to it.