Body Composition as Related to Heat Regulation in Women

¹ From the Department of Medicine, University of Illinois College of Medicine, Chicago, Illinois

Heat loss in psychrometrically controlled comfortable, cool and hot environments and basal heat production were related to body size and body composition in young, aged, obese and hyperthyroid women. Total basal heat production was equally well correlated with ‘lean body mass,’ ‘cell mass’ and surface area. The rate of basal oxygen consumption of ‘cell mass’ is not constant, being lower for obese than for nonobese women. The ‘cell mass’ basal oxygen consumption rate decreases curvilinearly with increases of body size (surface area) independent of body composition, and decreases curvilinearly with increases of ‘cell mass’ (as % body weight) independent of body size. There was no evidence of either decreased mean skin temperatures or rates of evaporative water loss per unit area in the obese women as compared with normals in cool environments. There was no evidence that the thicker layer of subcutaneous fat in obesity provides an insulating effect to heat loss. Hyperthyroid women had significantly increased mean skin temperatures and rates of evaporative water loss in cooling environments despite a need for restriction of heat loss. This suggests that under these conditions the changes may be concomitants of the hyperthyroid state which are not the result of excess heat production. There was a close relationship of rates of basal heat production and heat loss to surface area despite marked differences in body size and body composition. Surface area remains as an important and reliable parameter in studies of heat regulation in normal and obese women.

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