The metabolic rate and heat loss of fat and thin men in heat balance in cold and warm water

Abstract

suggested that deep cooling might be of little importance in practice. However, it has been reported (Keatinge, 1960 a) that although the rate at which men's rectal temperatures fell in water at 150 C was closely related to their subcutaneous-fat thickness, their early metabolic response to the cold immersion was not, and the metabolic rates of thin men only rose substantially above those of the fat men during the later part of immersions, when the thin men's rectal temperatures fell. The present studies of fat and thin men in a steady state of heat exchange in water were designed partly to confirm or refute this evidence that stimulation of deep temperature receptors plays a major part in adjusting the metabolic rates of fat and thin men to their different rates of heat loss during prolonged exposures to cold. They were also designed to show whether fat and thin men have different critical ambient temperatures, at which physical temperature regulation is complete and below which the metabolic rate is increased (Rubner, 1902;Burton & Bazett, 1936;Scholander, Hock, Walters, Johnson & Irving, 1950).It was hoped that these experiments would also show whether cold vasodilatation substantially reduced the tissue insulation of fat men in near-freezing water. This seemed probable, as cold vasodilatation takes place eventually in cold extremities of even generally chilled people (Keatinge, 1957) and appears to be due largely to the direct effect of low temperatures on blood vessels (Keatinge, 1958). Physical exertion accelerates the fall in the rectal temperature of thin men in water at 160 C (Pugh & Edholm, 1955) and in water at 5 and 15°but not at 25 or 350 C

Comparison of thermal responses between rest and leg exercise in water

“…Clearly, the exercising, limbs considerably increase the overall heat conductance (27). Considering these factors and research findings, several investigators have concluded that rest is more effective than armleg exercise in maintaining a higher core temperature when individuals are immersed in cold water (3,10,12,15).…”

The evolution of body fatness: trading off disease and predation risk

“…By virtue of its lower water content, fat tissue has a lower thermal conductivity than lean tissue (Cohen, 1977;Cooper and Trezek, 1971) and, hence, when fat tissue is distributed in a continuous subcutaneous layer (such as the layer of blubber in pinnipeds and cetaceans) it may provide substantial thermal insulative benefits. Studies of humans immersed in cool water (15-20°C) show that individuals who have greater adiposity cool down more slowly than leaner individuals and do not need to elevate their metabolic rate as much to defend this slower cooling rate (Cannon and Keatinge, 1960;Buskirk et al, 1963;Kollias et al, 1974;Keatinge, 1978;Hayward and Keatinge, 1981;Tikuisis et al, 1988;GlickmannWeiss et al, 1991). These studies indicate that obesity in humans also provides an insulative advantage.…”

Metabolic Habituation Following Repeated Resting Cold-Water Immersion Is Not Apparent During Low-Intensity Cold-Water Exercise.

“…Notwithstanding this lower T sk , more rapid convectional heat losses occur, with T c falling two-five times more quickly compared with that observed in air at the same temperature (Hong, 1984). When immersion is accompanied by exercise, the rate of T c decline is often (Cannon and Keatinge, 1960;Keatinge, 1961), though not always accelerated (Craig and Dvorak, 1968;McArdle et al, 1984). This disparity stems not only from differences in water temperature and subject adiposity, but from variations in both exercise intensity and mode.…”