My 10 hour fasted blood sugar used to be around 120 mg/dl. After a year of keto it dropped to about 95 mg/dl. After nearly another year it now is typically 65 to 85 mg/dl depending on my state of glycogen depletion. Fasting has been the most potent thing for bringing my blood sugar down. Even when my blood sugar was over 100 after 10 hours of fasting it would continue to drop over the first 4 or 5 days of a fast until it would be in the low 60s. And after each extended fast it would settle in at a slightly lower baseline. I expect that weight loss just through keto without fasting probably achieves the same thing. And exercise probably also helps. But I don’t lose weight fast on keto alone and I don’t exercise enough to produce the quick noticeable change in the way that fasting did.
My carb tolerance is improving more slowly and is still fairly low. When my blood sugar is down around 60 mg/dl I can eat 50 g of carbs in a meal and stay below 100 mg/dl. But when it is at 80 mg/dl that much carbs will shoot me up to 130+ mg/dl for a couple hours or more unless I exercise heavily.
My fasting blood sugar and carb tolerance both seem to be impacted by the amount of protein I eat. I have about 50 kg lean body mass and when I was eating in a more recommended protein range of 60-80 g daily both were noticeably better than they are now while eating ~140 g protein daily and using whey concentrate.