Gluten- and potato-free carb loading?

With this new low-carb-ish diet, one thing I do wonder about is exercise.  About a year ago I ran a half-marathon and was training to run Hood to Coast.  For the past few weeks I've barely been able to do a few laps around the local park without getting tired and out of breath.  A few miles into the 5-mile hike on July 4th, and my leg muscles were tired and achy.  This morning's 3-ish mile hike required a mid-afternoon nap.  (Granted, it's bloody hot in Portland right now, which isn't helping either.)

Bars and Gu and loads of pasta helped with all that running.  Obviously, that's not really an option now.

It's been pretty frustrating.  I know that my body is adjusting to the new food routine and that there are a myriad of other ways I can get carbs and find the energy to run.  We did try some delicious trail mix bars this morning on the hike (with dark chocolate instead of milk, of course), and Lundberg rice cakes with peanut butter are my new favorite snack. 

But with everything else I have to think about, that just feels like one more thing right now...  Patience patience patience.