My experience has been a little nuanced to what most of us tend to believe and follow, although the inference that over time fbg will come down does ring true and this might be the key. I agree that fasting numbers can be the last to come down.
I was getting numbers of around 5.4 and wondering how some were getting low 4's, sometimes late 3's. I was working out hard with cardio and eating real food low carb / keto. One of these things got my fbg lower:
- Removed Oats completely (direct correlation to drop in HbA1c)
- Increased resistance / weight training, reduced cardio
- Time and consistency
- Reduction in additional fat
I am not sure if there is a magic bullet. It might be residual insulin resistance that can keep fbg high.
The removing of any unnecessary carbs is an obvious win. The resistance / weight training is a proven glucose sink, with more surface area to independently of insulin uptake glucose. Time is probably a pareto item; "we" took decades to get IR /diabetes, it might take months or years of consistently doing the right things to regain low numbers - but in-between health still is improving. The reduction in fat is espoused by Dr Ted Naiman. His view is that the "extra" fat some do on low carb / keto produces increased glucose (from memory) 10 - 12 hours later. I think for some this true....not popular to say, but there is a reason why Dr David Unwin tends to exclude "high fat" from low carb, and I don't think this is just the politics. Dr Eric Westman says not to add extra fat on top of the fat the real foods come with. In short if you are having cheeses, creams maybe reduce these, for steaks, fish etc maybe go easy on the butter.
I go for a holistic approach with self experimentation - my current experiment, which was interrupted by severe Covid is muscle and protein centric Ketovore. On a normal day fbg is 4.4, on a bad day (can't get out to walk or do resistance) 4.7 and on an optimised day 3.8 - 4.1.
Then a carb meal at bedtime- porridge, bg was10.
