The women tend to be slightly anemic on arrival at altitude. The iron deficiency at the start results in them not reacting to altitude very well. Low Ferritin measures, below about 25 are suggestive of low iron stores. Even with good iron stores, it takes 6-12 months to see a meaningful increase in the number of RBCs. Living at altitude gives you some benefit racing against sea level runners.
Many people decrease food consumption due to suppression of appetite, and nausea.
The appetite change means lower glycogen stores. Your VO2 max also falls. Lactate levels at a set speed will of course be higher. Your threshold pace and VO2 max pace will be slower. There is a hormonal response to correct the glycogen situation, Catecholamines, epinephrine especially, is secreted.