That's a shame about your running. I know my mum sometimes braves the dark with the aid of a head torch. I was about to say that I wish I had a forest near me to walk but then I remembered I'm about a 10 minute train ride away from the Peak District. I definitely need to go sometime soon. Good job in the diet also! I'm trying to put/keep on weight so it seems our diets are quite opposite. It sounds like your job has got your work cut out for you. Good luck in the task, it always simultaneously amazing and slightly terrifying to be working on such a project that you describe.
I think by the time the diet is finished in a few weeks it should be bright enough to go for a quick run after work. Its more postponed for a bit rather than cancelled. The work project is a doozy on many levels but it is exciting. You need that fear to keep your head in the game sometimes.