> 1. High-fat diets, as done in your 3rd paper and as done in most "high fat" studies, are incorrectly labeled such. "High-fat diet (HFD, n = 10: 55 % fat/25 % saturated fat/27 % carbohydrate)"[0] is not what the parent meant by "reducing sugar and carbs altogether instead of promoting whole grains as they do." A more honest interpretation would be "max 40g carbs, the rest fats and proteins." This is because the main benefits of such a diet only come out when carbohydrates are severely restricted -- as has been known for a while now.

Where's the evidence? I linked to a study, one that isn't confounded by weight-loss (unlike the studies you people like to cite) demonstrating that as the fat (especially saturated fat) content of the diet increased to an absurd degree (55%!), insulin sensitivity tanked. Why would insulin sensitivity, when measured by an Oral Glucose Tolerance Test, suddenly improve if you restricted carbohydrate even further? Yeah, at some point your intake will be so low that you can "game" an HbA1c or fasting BG test, but underlying insulin sensitivity will be trash (which an OGTT would show), unless maybe you lose enough bodyfat to offset it.

Why do so many people on keto develop "physiological insulin resistance?" Why does all of the epidemiological evidence show strong inverse correlations between low-fat carbohydrate consumption (like whole grains and fruits) and T2DM, but the reverse for high-fat "carbs" like cookies or pizza?

The most reasonable interpretation of the data right now is that high-fat diets make you less insulin sensitive.