Unsaturated fats are called that because they have open bonds available; "monounsaturated" fats have one and "polyunsaturated" fats have more than one. Saturated fats -- animal fats -- have zero. Without machine processing unsaturated fats will all oxidize -- spoil -- and thus they are all processed to prevent that and make them shelf-stable.
When I went low-carbohydrate and then years later wrote this article documenting the results of my N=1 experiment (which incidentally, done correctly, is high saturated fat, moderate protein, low-carb) I accidentally, without knowing how dangerous these seed oils were (as I hadn't yet dug into that aspect of modern food being in many cases literal poison) also removed basically all seed oils from my food intake. Why? Because a steak, rack of ribs or chicken breast (skin on thank you!) has no seed oil in it. Yes, those animals eat plants (duh) and thus some of it is in their flesh but there is a balance to it. What I added to my green vegetables and eggs, either cooked in or on, was butter which is of course animal-fat based as are cheeses. Basically all of the inflammation-related things, along with the body mass, disappeared including some (severe allergies) that I had suffered from all the way back to childhood.
The bad part of seed oils is that they get incorporated into your cellular structure and the turn over has a half-life of about two years. This happens to almost-exactly align with what we've seen in chronic disease; we now have young adults in their 20s and 30s showing up with colon cancer, pancreatic cancer and similar, along with serious other maladies like Crone's. Chronic inflammation is known to be an actual cause of all manner of serious trouble including heart disease, cancer and more. Indeed lung cancer caused by asbestos isn't from chemical damage to cellular DNA because it can't be; asbestos was used because its chemically inert which is what makes it fireproof (it will not oxidize or otherwise react with other chemicals), including in the body. Because of that it causes inflammation the body cannot clear and that is why the cancer occurs. The medical industry knows this is the case yet they and the government refuse to at minimum label all alleged "foods" that are inflammatory when used on a regular basis as carcinogenic and ban those that are unreasonably-so and have non-inflammatory alternatives.
The facts are that if you remove them all from your diet now in a year or two a material amount of them will be gone from your body and that will continue to improve over the next 20 years (at which point there will be statistically none remaining; 10 half-lives is the mathematical formula for that.)
