Another idea for you. If after a week you still feel bad on your commutes, try eating half a sweet potato with some lean protein for your pre-ride meal. While for me even sweet potatoes raise my blood sugar, I notice its not as bad as other carbs. BUT really, you should have enough glycogen to ride 8 miles without Bonking. When you cut down on carbs, I hope you didn't cut down on protein too. If anything you want more protein, like at least 1 g per lb of lean body mass. You want your fat at about half that, and your carbs to be all you want of NON-STARCHY veggies, period.