This can make multitasking harder or easier. If tasks mesh well you can work on whichever you're better suited to at the time.
My ability to focus creatively or detailed seems to be directly tied to how well rested my mind is.
When I sleep and eat well it's far easier to concentrate and slip into flow.
It's Saturday and I woke up at 7, an hour before my alarm.. I've pretty much cut out all my caffeine, sugar and processed foods. The more I cut out our limit the more my energy soars. I have friends who found the same after citing back beer and certain meats. I'm the guy who lived to sleep in.
Either way I find my energy boosts are like CPU usage.
The less that is taxing my body by what I put in it and drain it with leaves more energy for all the tasks. It's borderline addictive to modify.