science

This study shows inflammatory markers are increased on a ketogenic diet: https://pmc.ncbi.nlm.nih.gov/articles/PMC6922028/

This rat study shows increased senescence in heart and kidneys in long term ketosis: https://www.science.org/doi/10.1126/sciadv.ado1463

However, Cholesterol is not a disease - its essential for life - the concern has never been cholesterol but atherosclerosis - if someone has elevated LDL, undamanged and unglycated (as on keto) and they are concerned they should get a CAC score so they can see their actual plaque burden.

What you're asking for is being studied. Here's a meta study from 2013:

However, one established risk factor of CVD, i.e. LDL-cholesterol, still turned out to be harmfully affected by the VLC regimen, most probably attributable to the larger amounts of saturated fat in the diet(Reference Bueno, de Melo and de Oliveira1). In their discussion, the authors stated that future meta-analyses should investigate the impact of low carbohydrates (LC) v. LF on other important pathological markers, e.g. endothelial function, in order to further assess the safety of LC dietary therapies.

This is reasonable, since evidence from prospective cohort studies has shown that endothelial dysfunction represents an independent risk factor for the development of many CVD including atherosclerosis(Reference Inaba, Chen and Bergmann2). We, therefore, carried out a meta-analysis to compare the effects of LC and LF regimens on flow-mediated dilatation (FMD). FMD of the brachial artery is a non-invasive measure of endothelial function, furthermore reflecting the local bioavailability of endothelium-derived vasodilators, especially NO. Inflammation of the endothelium is regarded to play a major role in the destabilisation of atherosclerotic lesions, therefore paving the way for future CVD events(Reference Inaba, Chen and Bergmann2).

Their results:

In our meta-analysis, LC dietary protocols were associated with a significant decrease in FMD when compared with their LF counterparts. A recent meta-analysis of observational studies including a sample size of 5·547 subjects has observed that a 1 % decrease in FMD is associated with a 13 % increase in the risk of future cardiovascular events(Reference Inaba, Chen and Bergmann2)

Along the same lines, here's another study with arterial measurements that shows reduced blood flow and arterial function for those who stuck with a high protein diet: https://journals.sagepub.com/doi/10.1177/000331970005101003

Look, none of these studies are, standing alone, enough to really change things. But it seems to me, from the outside that you're cherry picking your own results to justify carnivore diet.

The high carb versus low carb discussion is complicated and has a lot of factors at play. But the evidence for animal versus plant based low carb suggests that animal product diets are more harmful than plant product diets of similar macronutrient profiles.

Moreover, the overall trends show that those who eat a lot of whole grains (which are, by their nature, high carb plant based foods) have lower mortality than those who don't. The same is true of those who eat a lot of fruit (again, high carb plant based food).

Trying to tease out which of a million variables is truly responsible for cardiovascular health isn't easy, but a lot of the overall trends can be seen:

• Whole grains good
• Whole fruit good
• Red meat bad
• Cured meat really bad
• Seafood good
• Legumes good

Now, you can quibble with confounding variables, but at a certain point trying to argue that minutiae starts looking like religious apologetics, really cherry picking examples in favor while ignoring examples against. Coming up with a coherent theory of "fiber not important" or "the foods our genetic ancestors ate are somehow bad for us now" is an uphill battle, and I'm not convinced that the carnivore diet is anything more than a scam designed to sell books.