Managing blood glucose: Supplement Experiences / reversable?

Options
Okay, I'm on day 40 of Whole30 and realize the ONLY way to lose this weight is through diet and exercise. It's going great. I've lost 20 pounds or so and need to lose 20 more to be at high end of "normal" for my BMI - which to me seems skinny. I've gained and lost the same 30 pounds 5 times in the last 10 years, and I think that has caught up with me a bit.

I"M NOT interested in magic snake-oil for weight loss. However, even with eating 0grams of sugar, wheat, grains, dairy, beans or any processed foods for 40 days, my 12-hour fast blood glucose reading is 110 (pre-diabetic). I do eat some berries, but very few, and it seems like 12 hours should be enough to clear that out.

I am intrigued at the claims that cinnamon or green coffee bean can lower blood sugar, but I don't trust the "studies" that are published. I'm interested if anyone has had any real MEASURED success lowering blood sugar with supplements - or maybe I'm eating something still that would cause this.

Also, curious if losing 20 more pounds will improve my blood glucose readings - or have I screwed up my body forever to where I have to watch this like a hawk?

If you could post your EXPERIENCE managing blood glucose, I really would appreciate it.