"When you get up high, like 16,000+ feet, and if your appetite starts to wane, "
That night at 17,200', I was super hungry for some reason. The Chinese style soup noodles weren't that great -- but I ordered two bowls (double portion) anyway and wolved it all down. In other words, I completely ignored the guide's advice.
I felt no negative effect whatsoever, but posted the question because I could have just been lucky...
The suggestion to switch to simpler carbo makes sense!