Basal Metabolism and Heat Loss of Young Women at Temperatures from 22°C. to 35°C.

Abstract

Eight normal women have been studied in the calorimeter of the Russell Sage Institute of Pathology in regard to the mechanism of heat loss and heat production at environmental temperatures ranging from 22° to 36°C. The women were lying nude under basal conditions on a comfortable bed within the calorimeter. The results have been compared with those obtained on two men, using exactly similar procedure. The basal metabolic rate of the women in the colder zone was about 35 cal./sq.m./hr. and approximately the same as that of the men. In the warmer zone the women showed a marked drop in basal metabolism until it averaged 30.9 cal./sq.m./hr. at 31°C. The men showed no such drop. This indicates a type of regulation of body temperature which was not found in the men whose metabolism had remained level. In the women the fall in basal metabolism was concomitant with marked decrease in heat loss in the comfort zone, reaching at 31.5°C. as low a level as 28.5 cal./sq.m./hr. The lowest point observed for the men was 34.9 cal./sq.m./hr. In the warmer zones there was considerable variation in the individual response. The average skin temperature for the women in the hot zone was higher than that for the men by 1.5°C. and lower in the cold zone by 1.0°C. The conductance of the peripheral tissues for the women was 20% lower than that of the men in the cold experiments, representing 20% more insulation against cold. Sweating was less marked in the women and did not begin until the environmental temperatures were higher than was the case for the men. In general, there were slight differences in every single factor of temperature regulation, and in all respects the women had physiological advantage, but especially in the reduction in heat loss and heat production in the warmer comfort zone.