Effect of acute exposure to reduced atmospheric pressures on body weight, food intake and body composition of growing rats.

Growing male rats were exposed to simulated altitudes of 1850, 2900, 4100, 5450 or 7100 m in a hypobaric chamber to determine the effects of altitude on body weight gain and food intake as function of time of exposure. Female rats were exposed to a simulated altitude of 7100 m for 24 h to determine the effect of altitude on body composition. The results obtained indicate that in growing rats exposed to acute simulated altitude the initial body weight loss and the depressed growth rate, on one hand, and the reduced food intake, on the other hand, are related to the degree of the altitude; the parameters are not affected at altitudes below 1 850 m; the initial weight loss is not solely due to reduction in food intake, the additional loss being attributed to the added stress of hypoxia; the body weight loss occurs without marked alterations in body composition, although a tendency to dehydration exists; and the body compositional changes are the reflection of the altitude-induced hypophagia.