When I started potato starch about 2 years ago it caused a dramatic improvement in my 90 minute post-prandial readings after about 50g of carbs, from the 120s to the 90s . (I was showing signs of pre diabetes, with a 1 hour OGTT of 200). It caused some reduction in my fasting glucose too. (90s to 80s).
For a couple of years my BG would still spike to 150-160, 45-60 minutes after a meal with 50g of carbs, unless it was just after a workout. (in which case It would only hit ~120)
The past few months my 45 minute post meal BG is in the 90s(!). The change was I have been taking half of a 12g Iodoral once a week, daily astaxanthin, as well as inulin and acacia powder to go with the potato starch (the latter 3 are all potent prebiotics). And also 5,000 D3+K2 which I've always taken. I stopped taking my 500g 2x/day Metformin as an experiment, and also stopped cinnamon and Chromium supplements, with no change after 3 weeks.
I can't tell you if the astaxanthin has anything to do with it, but there are a few anecdotes that iodine insufficiency can affect BG.
Other than that, I eat moderate-carb paleo (no industrial seed "veggie" oils, no grains e.g. flour, very little processed food, little sugar), and I get most of my starch from white rice or tubers/potatoes/yams.
Apparently there are 11 sub types of diabetes according to this author:
.. and I suspect I have mild liver insulin resistance, no muscle insulin resistance, and an issue with the "incretin effect" (which is helped by prebiotics).
The above 11 types is probably why some things work for some but not all people. So I think anyone who really wants to improve their condition needs to experiment.
P.S. I plan to resume taking Metformin due to its anti cancer and longevity effects.
P.P.S. I've never had more than about 20 lbs of excess fat. But now I don't have any.