Does an hour of sitting erase 8% of your 60 min run? This article addresses this question. I'm not sure the algorithm they used to get to these results, but makes you think.
Running and Sitting.
The brain is a powerful thing. A lot of research is being done that shows that your body starts to fatigue when the brain feels like your reaching a limit and it doesn't want to risk health. The problem is that it does this way to early. If you can convince your brain you are fine, you can keep going at a higher level. Convince the brain.
Can particular foods or diet help with food? I personally have a very small bowl of ice cream an hour before I go to bed. Food and Sleep.