We were both very deficient in the 4 big electrolyte minerals: magnesium, potassium, sodium and calcium. Those were the big ones - magnesium is pretty important in thyroid function as well as mitochondrial energy production, and they all counter-balance each other so it's easy to get unbalanced. We were doing a LCHF diet for a while, with intermittent fasting and an occasional longer fast of 24-48 hours, and what we didn't know is that as you loose glycogen and shed water weight, all of those minerals leave with it. After 4 or 5 months we were starting to feel the effects of being chronically deficient. You really need to be supplementing those minerals (at least) if you're going that route. But pretty much everything was wonky, because our bodies weren't absorbing everything we ate because some of those are necessary for absorbing other nutrients.

We cooled off on the aggressive calorie reductions and focused on getting those minerals basically. We started supplementing them to get back into reference range, and then basically picked and chose foods based on their mineral contents. A lot of leafy greens, nuts and seeds, and then dairy and fish (we were buying canned sardines in bulk because we were afraid of the mercury in tuna and other larger fish).

We make ourselves an electrolyte blend most days and sip it if we're feeling lethargic in the middle of the day, and it is amazing how much of a difference it makes. Once you learn what it actually feels like to be unbalanced, it's quick and easy to fix it.