I watched a survival video produced in Sweden in which the host purposefully goes without food for most of the trip. At one point he tests his blood sugar, then brews some spruce tea, and tests his glucose levels once more. The results were surprising... To me at least. His blood glucose levels improved.

You can find the videos at The Swedish Wilderness Survival Project Site

On a side note, I believe all of the videos are worth watching, even when you have to read the subtitles. <img src="/images/graemlins/grin.gif" alt="" />