Energy metabolism increases and regional body fat decreases while regionalmuscle mass is spared in humans climbing Mt. Everest

The objectives of the study were to determine regional changes in body comp osition, energy expenditure by means of doubly labeled water, and net energ y balance during exposure to high and extreme altitudes (5,300-8,848 m). Th is study focuses on a subset of subjects who consumed the doubly labeled wa ter (three base camp personnel and seven climbers). Regional body compositi on was determined by measuring skinfold thicknesses and circumferences at 1 0 different sites on the body. Energy expenditure was measured by doubly la beled water excretion. Discrepancies between actual energy expenditure and data obtained from diet records and body weight changes suggested a chronic underreporting of dietary energy intake, especially by those subjects who reached the highest altitudes. This underreporting may be due in part to di minished cognition or to a preferential focus on survival, rather than on f illing out diet records accurately. Mean adjusted dietary intakes were 10.5 0 +/- 0.65 MJ/d (2510 +/- 155 kcal/d) for those who remained at base camp, and 20.63 +/- 6.56 MJ/d (4931 +/- 1568 kcal/d) for those who climbed above base camp. Energy expenditure averaged 2.5-3.0 times sea level resting ener gy expenditure. Differential changes in regional body composition suggested a preferential loss of fat mass and a relative sparing of muscle mass, des pite insufficient energy intake to maintain body weight.