Metabolic aspects of acute altitude exposure (4,300 meters) in adequately nourished humans

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Abstract
The daily calorie consumption in human subjects can be maintained after abrupt exposure to high altitude, providing that the men are in good physical condition prior to and during altitude exposure. This study indicates that a) positive nitrogen balances can be achieved during altitude exposure; b) body weight losses can be greatly reduced; c) mineral balances are positive; d) blood electrolyte levels are normal; and e) fasting glucose levels and glucose tolerance curves are normal. Normal digestion and absorption also occurred during acute altitude exposure. It appears that many of the biochemical changes, previously attributed to hypoxia, that occur during abrupt high altitude exposure, may be the result of anorexia and the subsequent caloric restriction. Hypohydration occurs during the first days at altitude whether intakes are adequate or not. This appears to be an effect of hypoxia, and may be an adaptive response of the body under these conditions.