Speaking as someone with familial hyperlipidemia / hypercholesterolemia and based on many years of conversations with multiple lipidologists…
Heterozygous FH will typically put someone at a total cholesterol roughly around 500mg/dl, and homozygous will get them closer to the 1000mg/dl mark. Dietary factors for most people will affect their lipids up to +/- 40mg/dl, and medication is generally required for anything beyond that.
For the gentleman with cholesterol nodules, that’s a not-unheard of symptom of homozygous FH and the associated cholesterol levels. I’m sure his diet is exacerbating it, however I would be genuinely surprised if that were the primary cause of his count being > 1000mg/dl. (With homo-FH and an extremely restricted diet, he’d still be unlikely to get below 900mg/dl)
Anecdotal, but if you follow carnivore diet groups on Facebook/IG etc you'll frequently see posts from people with TC over 500mg/dl. For example, the carnivorecringe IG account posted someone's labs in December who had a TC of 669 and an LDL of 558.
It's quite possible that it's a combination of diet and genetics, but people can quite easily get to incredibly harmful LDL levels with diet alone.
Edit: here's a case study of someone getting to TC of 488.7mg/dL. I think you'll struggle to get higher quality data than case studies because these kinds of diets are (thankfully) fairly uncommon and no ethics board is going to sign off on an intervention study that's likely to raise blood lipids by this kind of level.
Edit: misread your comment, apologies… I’m not sure about inducing it in people based on diet, as that seems to go against any desirable outcome, but this is a link to another FH case presenting cholesterol nodules:
Heterozygous FH will typically put someone at a total cholesterol roughly around 500mg/dl, and homozygous will get them closer to the 1000mg/dl mark. Dietary factors for most people will affect their lipids up to +/- 40mg/dl, and medication is generally required for anything beyond that.
For the gentleman with cholesterol nodules, that’s a not-unheard of symptom of homozygous FH and the associated cholesterol levels. I’m sure his diet is exacerbating it, however I would be genuinely surprised if that were the primary cause of his count being > 1000mg/dl. (With homo-FH and an extremely restricted diet, he’d still be unlikely to get below 900mg/dl)