Alterations in body composition in man after acute exposure to high altitude

Abstract

Body composition was measured in 5 young males, residents of Denver, Colorado (5,280 ft altitude) before, during, and after 8 days on the summit of Pikes Peak, Colorado (14,100 ft altitude). Body weight progressively decreased during the altitude period resulting primarily from a decrease in body fat as estimated by measurements of body density, creatlnlne excretion, and total body potassium (K) (from K40 counting). No changes were observed in total body water (W), lean body mass, protoplasmic mass (M3), and bone mineral all of which were derived from the same measurments. Although M3 was unchanged, calculations based on creatinine excretion and K showed an increase in nonmuscle protein at the expense of muscle protein. Attempts to measure W directly, employing deuterium oxide dilution, were unsuccessful possibly due to uneven distribution of this isotope in the body water compartments at high altitude. A highly significant decrease (P < 0.001) in plasma volume after 4 and 8 days at altitude provided direct evidence for altered water distribution in this environment.