I think that ME/CFS is characterized by low dopamine production. Dopamine is the activating chemical. It is often referred to as pleasure giving but it also can speed and lift the energy of the brain. Salt increases dopamine. Sugar will too but the trouble with some of us with ME/CFS, or at least those like me, is that there is a problem with sugar processing. To me it feels like a monkey wrench in the works—a spanner in the works, if that is UK talk. Maybe this problem with sugar processing has to do with the body’s move towards a Plan B anaerobic energy production. But salt, again in my case, will do the trick—it gives me a little sense of pleasure and increased alertness. Salt, and a lot of it, is also helpful for my very low blood pressure.
As for protein, it provides carnitine and enables the brain to get tyrosine which activates the brain. I need to look up the relationship among carnitine, tyrosine, and dopamine—or one of you can probably explain it. Tyrosine in my experience and to my knowledge generally also has an anti-depressant effect, good for Seasonal Affective Disorder which I would otherwise get.
Carbs—leaving aside the sugar processing issue— result in more tryptophan then serotonin. This has the opposite effect of tyrosine. Serotonin might make someone feel calm or sleepy or slowed down—a desired effect later in the evening. It can also help some with pain relief.
I have read that it is better to have protein in the morning, mostly protein, and to skip the carbs until sometime later in the day, and that this gets the brain more activated as well as sets the body’s expectation low for having to put out a lot of insulin, then getting the body into an up and down pattern with blood sugar and insulin during the day, but that is going into another subject.
Main thing is—I agree that salt, fat and protein are helpful!