In my opinion and experience I would have to say both because for your body to keep and obtain maximum health you need to ...
1. Fuel it with quality food (not sugar-filled processed junkfood) and vitamin/mineral supplements as a booster.
2. Sleep or at least take 'nanna-naps' and rest throughout the day.
Preparing and eating good quality proper food can be a struggle when you are run-down and tired because it is easier to just grab a take-away or packaged product but all it does it hype you up for an even bigger fall as your body becomes sugar-dependent.
Personally, there are days that I would kill to be able to sleep for a full 8 hours, but until I can I do the best I can by taking 'time-out' throughout my day to rest, to stretch my body and if able to go for a walk or do some light exercise just to help tire me out.
All the best. :-)