> "If you just reduce overall fat, you may even be making that P:S ratio worse."

Ugh.

> "There’s no evidence that oxidised fats in unsaturated fats are a cause for concern for health."

https://openheart.bmj.com/content/5/2/e000898 says: "The low-density lipoprotein (LDL) oxidation hypothesis gained traction during the 1980s because it was noted that in general, native unoxidised LDL does not cause foam cell formation. In other words, LDL had to become oxidised first in order for atherosclerosis to develop [..] what causes LDL to become oxidised in the first place? It was later discovered that the oxidation of LDL was initiated by the oxidation of linoleic acid contained within the LDL particles [..] a more comprehensive theory, the ‘oxidised linoleic acid theory of coronary heart disease’, is as follows: dietary linoleic acid, especially when consumed from refined omega-6 vegetable oils, gets incorporated into all blood lipoproteins (such as LDL, VLDL and HDL) increasing the susceptibility of all lipoproteins to oxidise and hence increases cardiovascular risk [..] cholesterol was protected from oxidation if bound to saturated fat but susceptible to oxidation when bound to linoleic acid"

That is condeming oxidised serum fats, not oxidised dietary fats, but it appears to be condemning "omega-6-rich vegetable oils" in the diet because they are more likely to oxidise in the body(?). I'm guessing if they are already oxidised when eaten that matters, because the only way it couldn't matter is if we deconstructed fats we eat and rebuilt them completely from scratch and if we did that completely then none of any of this would matter. The link's Box 1 has 29 points criticising those fats, Box 2 has 1 point in their favour "reduces total cholesterol and LDL".

> "Aside from that I don’t think stringing together a bunch of mechanisms and speculating about them is a particularly useful way to carry out science."

Well I'm not gonna understand biology, chemistry, lipid science to the level of a PhD researcher, PhD statistician, medical doctor, or an interested smart amateur biologist/chemist, myself. If I also can't have a bro-science chain of layperson reasoning, then your position boils down to "Science is only for experts, and only the experts I choose, not those they believe the wrong things so they're quacks, trust me" which is .. disagreeable.

> "What we care about is actual outcomes from actual interventions."

We can't see those until people don't die of heart disease fourty years later. This is why I'm so on the side of Dr William Davis because the CAC score seems to be the only good non-invasive measure of plaque available, something which can show an almost direct outcome of intervention on plaque. Whereas "serum LDL went down" is easily measurable but doesn't show if plaque formation is slowed, stopped, reversed, or unchanged. I also think that if low-fat did avoid or reverse heart disease, the massive international push over the last 50 years for low-fat foods would have made it absolutely clear, and instead heart disease is up up up. Doubling down on "people simply didn't eat low-fat yoghurt hard enough, do that harder" is just so unconvincing.

> "But we also know that fat quality affects CVD risk too"

When you say fat quality, do you mean PUFA vs SFA? Or do you mean things like presense of Glyphosate, trans-fats, contaminations in the food chain, things ordinary people mean by quality?

> "and by a decent amount. So within whatever dietary pattern one settles on, replacing SFA with PUFA would also be a good idea. We can do both!"

You've made a strong case that reducing serum cholesterol would be a good idea. Not such a strong case that reducing dietary fat would be a good idea. And not much case at all that replacing SFA with PUFA is a good idea. Let's be clear that I'm lost in the details of SFA, PUFA, linoleics, Omegas, LDLs/HDLs, triglycerides, cholesterols, which ones are more important, which ones are a tiny effect but easier to study or more interesting to study. When someone is 150lbs overweight and insulin resistant and never does an exercise it can't possibly come down to wibbling over whether they ate two slices of bacon vs half an avocado, or whether they put butter or margarine on a scone that one time. On the other hand if someone is Mark Sisson[1] a lean former ironman runner and paleo/low-carb enthusiast who got famous for eating a "big-ass salad" everyday, who does intermittent fasting, eats salmon and leaves with avocado oil dressing for lunch, then a ribeye stake with asparagus and avocado for dinner, no snacks, no desert, who cares about health, is he at risk of heart disease because he put heavy cream in his one coffee of the day and has red meat on his plate instead of nutloaf?

I guess you're suggesting to remove a daily Starbucks coffee with whipped dairy cream and sugar, right? No-brainer, I would agree.

But telling Mark Sisson to replace that steak with tofu? He has solved or avoided so many other problems people have with food - no food cravings or hunger, he's not overweight, he's not fatigued or big swings of energy, he's unusually healthy for someone in a Western country at his age (50s IIRC) that he's gotta be doing a lot right, not a lot wrong. He's gotta be somewhere close to a good human diet even if that is too much meat to eat every day for other reasons.

[1] https://www.youtube.com/watch?v=knbo9Tw2b9g