> If it is settled science, I would hope you could find and share authoritative evidence that it is. What I’ve seen over the years (and I’m not that old) is that the mainstream “consensus” changes every 10-15 years
The nature of science is that consensus adjusts to data. But unless something is a very new field of research, there typically aren't major shifts in consensus. The scientific process is more akin to incrementally washing away layers of misunderstanding. Within the context of cholesterol and heart disease, we've been washing for over 100 years[1], and the consensus on that connection has been unwavering since the 1950s.
Research in the late 1950s actually hinted at trans fats being the culprit, but then came the aforementioned period of anti-fat political manipulation, so it wasn't until the early 1990s when new studies built on the 1950s research and solidified scientific consensus. That consensus eventually led to federal policy changes and the banning of trans fats, which has since resulted[2] in an estimated ~4.5% reduction in heart disease mortality and an ~8.9% reduction in stroke mortality.
Since those studies in the 1990s, consensus hasn't changed and is quite simple[3] to understand. LDL greatly increases risk for heart disease and stroke. HDL absorbs LDL on its way to the liver, lowering LDL levels. Trans fats contain only LDL and are thereby inherently harmful and deadly. Saturated fats contain more LDL than HDL, but their ultimate effect on the total HDL ratio and mortality is negligible. Unsaturated fats contain only HDL, making them inherently healthy presuming an appropriate level of consumption.
Those are all facts. There is no current research refuting any of it, meaning we are at a stable point in scientific consensus on the subject.
> I’m with you that some level of fat intake is healthy and that sugar/starch are suspect, but I just think it is dishonest or misleading to say it is “fact” or settled science given the uncertainty and ongoing changing nature of the scientific findings.
Again, you're eliminating the possibility for the concept of factual information to exist. Science is always ongoing, but that doesn't mean we don't have any established consensus.
A very long time ago, the extent of our chemistry knowledge was that water made things wet and we must consume it in order to continue living. These days we understand thousands of concepts related to physics and chemistry, nearly all of which have scientific consensus. But if someone today started adamantly claiming that pure water is acidic, that wouldn't make our current understanding uncertain or any less factual. All it would mean is that someone ignored the established consensus and expressed a personal opinion. It doesn't qualify as science and doesn't have any legitimate bearing on practice or policy.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3108295/
[2] https://cadmus.eui.eu/bitstream/handle/1814/31898/MWP_2014_1...
[3] https://www.hsph.harvard.edu/nutritionsource/what-should-you...