@RandomLondoner
When I was a kid I used to refuse margarine because I thought it tasted like plastic. As an adult I discovered that their chemical formulae only differ by something like an atom
Whereas butter differs from plastic by two atoms.
OK I made that up. But I doubt that two products that have such similar properties are massively different from each other, from an organic chemistry point of view.
Ok bear with me because my 30 year old a-level chemistry is somewhat rusty and there will be REAL chemists around.
They are very different by composition. Saturated and unsaturated fats are common parlance - and in its simplest form, this is what it means.
CO2 (carbon dioxide) - carbon had four electrons and oxygen had two. That means if you join a carbon atom it “needs” two oxygen atoms to be “saturated”.
CO (carbon monoxide) is an oxygen atom short - ergo it’s unsaturated.
Saturated is like going to a dinner party full of couples.
Unsaturated is going to a dinner party with one single.
Poly-unsaturated is BEING that single on a group holiday and expected to look after all the couples’ kids.
“Shitstorm”. 
Fwiw my mum was type I diabetic, was told to fill up on toast, cereal and plenty of healthy fruit juice.
I’ve struggled with my weight and have been told lots of pasta, tatties and bread (with marg natch).
One of my best friends is a medic and was taught the carbs first mantra - she truly believes it. As for the uni dietician degree - imagine the disappointment to have spent 3 years being fed BS - whatever happened to higher education encouraging independent thought?