Testing and diet

Recently there have been a number of posts recently that seem to suggest a lot of people are eating something, getting a high reading after but then eating the same thing on a different day.

So. How many people use their testing results to modify what they eat? If you test but don't use that number for anything, why? Is it because you don't really know how to use the test results? Is it because you don't know what a high number is? Is it because you can't live without that particular food? Something else? A combination?

I'm just curious because it seems that using testing results is not widely taught by doctors.