Bill, in healthy adults, insulin is secreted to remove excess glucose from the blood, so, if I'm hearing you correctly, you're basically asking if longer fermentation favors glucose production.
Yes, longer fermentation favors glucose production.
Glucose is being generated by enzyme activity. While enzyme activity does slow down at lower temperatures, it doesn't slow down as much as yeast does, so lower temps favor glucose production rather than glucose consumption by the yeast. In longer room temperature fermentation, less yeast is added to the dough. Less yeast translates into lower yeast activity/lower glucose consumption and favors glucose production. In other words, anything that curtails or slows down yeast (less yeast in the recipe or lower temps) favors enzyme activity/glucose production. Take away or handicap the predator and you'll end up with an abundance of prey.
Now, malted barley is an enzyme powerhouse, so the trend towards excess glucose formation is far greater in malted flour doughs, and, although longer fermentation definitely contains more residual glucose, it may not be all that much. It encourages browning, but it's generally not the kind of browning one witnesses with higher quantities of sugar that one finds in sweet doughs, just a little more browning than one finds in quick ferments. If I had to guesstimate, I'd say if a 2 hour ferment produces 0% residual glucose (in short ferments, yeast frequently consumes all the available sugar), a 24 hour dough with the same final volume (using less yeast or lower temperatures) would be somewhere in the 1% residual glucose realm. In other words, I don't think a long fermentation bread is going to shoot up the glycemic index.
