OPERATION EVEREST II: Effects of a Simulated Ascent to 29,000 Feet on Nutrition and Body Composition

Progressive body weight loss occurs during high mountain expeditions, but whether it is due to hypoxia, inadequate diet, malabsorption, or to the multiple stresses of the harsh environment is unknown. To determine whether hypoxia alone causes such body weight loss, six men were studied during progressive decompression to 240 torr for 40 days in a hypobaric chamber where hypoxia was the major variable. The subjects were provided a platable ad libitum diet that was modified for individual preferences. Complete food consumption data were available for only 38 of the 40 days. Mean caloric intake for 38 days at altitude was 2639 or - 848 kcalday Mean or - SD. Caloric intake decreased 42.3 from 3136 kcal during the first 7 days of exposure to altitude to 1789 kcal during the last 3 days at 282-240 Torr. During the same time periods the carbohydrate CHO intake decreased from 62.1 to 53.2 p 0.001. All subjects lost body weight with a mean loss of 7.44 or - 2.24 kg 8.90 of the initial body weight. Loss of body weight was greater than could be accounted for by comparing calculated energy expenditures to actual caloric intake. Keywords Body composition, Percent body fat, Hydrostatic weighting, Acclimatization, High altitude, Nutrition, Food intake, Weight loss.