I had good luck early in my running with heading out in the morning on an empty stomach. Found the energy somewhere and managed to get through the runs. In fact I'd even read that it can be beneficial... after a good night's sleep, your glycogen stores are drained, so your energy is coming entirely from fat!
Up at 5.30, running by 5.45, showering by 6.30... Perfect.
Tried it today for the first time since before Christmas. WOW. What a surprise. I had no pace... was supposed to do a 6K tempo run, which for me means running at about 5:20/km... I couldn't touch it, was closer to 5:45/km or slower, almost LSD pace.
Lesson learned. Body needs fuel. I'll be taking a bottle of Gatorade to make up for my depleted glycogen from a good night's sleep. Might scarf down a granola bar or something too.
I may not burn as much fat as I could, but if I can't run at a higher intensity I might as well stay in bed.