I'm not a KOOK - rather a convert to non-GMO foods. And I was able to prove this scientifically.
For me, personally, I can eat pretty much anything - and there is very little effect on my blood sugars. I am not diabetic. Mr. Peel, is NOT overweight and is VERY diabetic. (He's been needing up to 5 injections of insulin a day). The moment we dropped the synthetic food stuffs - the High Fructose Corn syrup, the spenda, the GMO-soy, the canola oil, etc, etc, his blood sugar numbers corrected themselves and he drifted toward normal.
You can give me a piece of Pepperidge Farm Rye bread, and my blood sugars numbers will moderately rise (as to be expected). I will start about 101 - go to 120, then an hour later, I'm back to 105 or so. Mr. Peel would start about 138 jump to 198-205, and stay that way for at least four hours later. The added junk in processed foods causes his body to panic - its as if he is having an allergic reaction.
What started us on this tact was a massive stroke he had 8 years ago. We never knew he was diabetic; it was undiagnosed diabetes that caused the stroke, and it is the junk in the foods that affects him terribly.
Your reaction to bread does not have anything to do with GMOs. No wheat flour is from GMO wheat, at least not any in the US. As far as I know, there is no such thing as GMO wheat.