Good day!

Running fasted: Would it be easier now I'm eating primally? Would I have to reduce mileage initially? I have run upwards of four hours before on just breakfast, so I'd like to think i'm very much fat adapted now. Also, I don't want to set out on a run, only to get half way round and just die a carb-like death. My runs are hilly, offroad, LSD, for around 1h:40mins, with very comfortable breathing, sometimes through the nose. (ego boost: I'm not slow!) Any help would be appreciated. Also, I apologize if this has been a topic before.