As more people make the move towards healthy unprocessed food diets I think its important to remember when you remove foods good or bad they can also have positive and negative effects on the body.
For me it’s been sodium and potassium balance due to almost completely removing processed carbs from the diet, sodium was something I’ve had to add consciously add to my day in the form of Himalayan sea salt and can tell the difference in energy and fluid retention when I forget to take enough. Subsequently I drink quite a bit of coconut water which is high in potassium leading to an even greater imbalance. I recently found this article which seemed to link these together quite interestingly and highlighting some other body functions that can also be affected.

http://www.ei-resource.org/articles/chronic-fatigue-syndrome-articles/nutritional-considerations-in-chronic-fatigue-syndrome/