JoannaS said:

 The fat eaten with it also had an effect, the more fat in the food the slower the spike – not that is necessarily a good reason to eat more fat but it shows how different foods have a different effect in combination. 

Daughter (who is resistant to insulin and therefore has to be careful with diet) discovered that ice cream is much less damaging to eat than cake for this reason.

Somewhere I read recently that the diet guidelines for diabetes are under review, and will be re-issued next year, probably taking glycemic load into account so they will look very different. Eating well rather than following out-dated information makes sense! 

I agree with everyone about not making yourself ill to prove anything to the doctor! The only benefit of being diagnosed coeliac is that you get a bit of GF food on prescription, but talking to people in the past what was available wasn't very good, certainly not worth months of suffering for.

Good luck with it all.