hey fellow bugster, i would say its because its a new activity and your bgs will stabilise as your body gets accustomed to the running, i have found a general reduction on average since the running and a definate hike when i stop and dont run for a week, so on average when your a little more used to it i think your average bg will be better than normal, for a 5k run or 30 minutes (ish) i wouldnt worry about eating until after the run if its early morning, i dont think its far enough for the body to need help, i think youd have enough stored energy.
absolutely nothing ive said can be considered advice mate, i have no knowledge about this medical or otherwise hehe, its pure conjecture
best of luck with the c25k program, ive heard its very successful :thumbup: