"We found that in elderly whose insulin sensitivity was still high, the brains were larger, and they had more grey matter in regions that are important for language skills, compared with those who had diminished insulin sensitivity. We also observed that higher insulin sensitivity was associated with better scores on the language test. Our findings offer a possible explanation for why methods that improve insulin sensitivity, such as exercise, are promising strategies for counteracting cognitive aging late in life," says Christian Benedict.
Of course insulin resistance is complex - not just about eating too many carbs - and Stephan's series is a great outline of the issues. Again, environment, genetics, gut flora are all kicking around but a real food diet, rest, exercise and reducing stress all help keep you sensitive to insulin.