This is the most dramatic change I've noticed since diagnosis 3 months ago.
When I was diagnosed with diabetes 3 months ago, I immediately changed what I was eating to keep my blood sugar in the normal range (not diabetes normal, but true normal). and it has made a very dramatic difference on how well my brain functions! I knew I had been in a fog for the last couple of years - I attributed it to exhaustion (my job demands about 60 hours a week, sometimes more).
* I noticed immediately how much more clearly I was able to think.
* In addition, it was pointed out to me that my affect changed dramatically at one point (I hadn't noticed). Once pointed out, I realized I suddenly felt exhausted. I tested my blood glucose and it was in the 130s (above normal, not terribly high, but 20% above the average for the preceding few weeks). A couple of days later I noticed the same phenomenon - suddenly I felt exhausted, I tested, and again it was above 130.
The second correlation was much more dramatic, and surprising, but it fits nicely with this study. I had not decided yet whether my dietary change (to Low carb, moderate protein) was permanent, but these two things I've noticed are certainly pushing me toward making it permanent.
(Although I do hope that over time I can tolerate moderately larger quantities of carbs without bumping my blood sugar up).