ABSTRACT
The acute physiological response to hypobaric hypoxia encountered at elevations above 10,000 feet has significant nutrition implications which have generated a body of ‘‘conventional wisdom’’ about the long-term effects of such exposure on nutrient need and energy substrate utilization, a conventional wisdom that needs to be reconsidered. Acute altitude exposure is associated with a cachexia due in part to loss of appetite. Under such circumstances metabolism may be biased toward catabolism of body protein and fat stores, resulting in body wasting and use of less oxygenefficient fuels. Accordingly many of the ‘‘chronic’’ physiological responses in energy substrate utilization attributed to altitude exposure may really be a consequence of malnutrition. Recognizing the confound presented by this situation to the understanding of true physiological response to hypoxia in our experiments, we have imposed nutritional control sufficient to maintain body weight and protein and fat stores. Thus, cachexia and malnutrition are differentiated from the other metabolic responses to hypoxia. Under these circumstances, altitude exposure shifts energy substrate utilization away from fat and protein and toward carbohydrate dependence.
† Deceased.
