Epidemiological studies suggest that insulin resistance accelerates progression of age-based cognitive impairment (…) Across the life span, brain network destabilization correlated with decreased brain activity and cognitive acuity. Effects emerged at 47 y, with the most rapid degeneration occurring at 60 y. Networks were destabilized by glucose and stabilized by ketones (…)
https://www.ncbi.nlm.nih.gov/m/pubmed/32127481/
Many of us here had a feeling this was true.