>>111061>>111116Ok I typed that because I was on my phone and that made me lazy but I do want to write my thoughts (previous pic related) even if you think I'm a crazy Peater or whatever
A fatty acid is essentially a carboxyl group (O-C-OH) bound to a hydrocarbon tail, that tail is "saturated" when every carbon in the tail is bonded to as many hydrogens as it can fit, and "unsaturated" fats have carbons that could bind to another substance. The fewer hydrogens that are bonded to the tail, the more "unsaturated" they are. A fat missing one hydrogen bond is "monounsaturated" and if there are two or more that are missing then the molecule is "polyunsaturated" (PUFA stands for "polyunsaturated fatty acid").
The reason that the polyunsaturated fats are bad for consumption is because the spots where the hydrogen is missing gives them a propensity to react with other substances in the body such as proteins, denaturing them and thus placing a chemical stress on the body's integrity. These reactions occur well below human body temperature, and the effect is so pronounced that the body will refuse to burn them for energy and prioritize burning saturated fats instead (since PUFA can damage the mitochondria), so an increased presence of the polyunsaturated fats actually lower the metabolic rate.
Seed oils (and fish oils too, but no one talks about them) are composed significantly of the polyunsaturated fats and they are bad basically for the reasons I've stated, but most people who are against seed oils don't really understand this kind of chemistry, only citing that they are "processed" or "unnatural" (lame handwaves for health influencers that don't understand what they preach)