I'm not an MD, but I want to reiterate what I've said before. IMHO, it is important to get enough sugar and salt (as well as water) when you might be dealing with altitude effects. Altitude changes are no occasion for fasting or low carb (or low salt). All of these things keep your blood volume and blood sugar up which helps the body deal with altitude effects.
One of my own altitude coping signs is that I get hungry for cheap calories I normally never eat. I have also learned that if I indulge that hunger the eventual symptoms will be worse and will include nausea, headache, "heavy chest" sensation and general logyness.
I have told pretty much everyone to just stop me outright if they see me diving into the choccy macadamia bag or the beef jerky bag or the protein bar stash, knock it out of my hand if they have to.