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high BW set-point, with dire implications for heat dissipation during the day. Even excessive use of air-conditioning might make heat adaptation and successful thermoregulation difficult.

It's Not the Heat, It's the Humidity

We think of high humidity as impairing our ability to perspire; humidity ought to impair heat dissipation and render the "functional temperature" even higher (for an overview see Burse, 1979). Heat combined with humidity should have a greater suppressive effect on appetite than dry heat. The anthropological evidence is confusing on this point. In Africa, humidity tends to be associated with a shorter, fatter physique in the native people, whereas in more northern climates (for example, Scandinavia), the wetter west coast breeds taller, thinner people than does the drier interior (Beller, 1977).

Gender Differences

There is reason to believe that men may be less heat tolerant than women. Beller (1977) notes that men have more, and a higher proportion of, metabolically active tissue than do women, who have a higher proportion of fat, and suggests that women's relative metabolic inactivity buffers them from heat stress. Beller goes even further and argues that women's extra fat tissue literally buffers them, by insulating them, from the external heat. It makes sense that a layer of fat might insulate one's internal core temperature from external heat sources; but such insulation should also make it more difficult to dissipate whatever heat is generated internally, through metabolism. Beller's conclusion is disputed, although not cited, by Burse (1979), who enumerates the physiological disadvantages of women working in the heat and urges that extreme caution be taken to prevent heat exhaustion in unacclimatized women.

Stress

Under acute stress, body temperature may rise. For example, boxers before a bout have a higher body temperature than they do before a routine practice. Mrosovsky (1990) refers to this temperature shift as psychogenic hyperthermia and attributes to it an enhancement of muscular activity. "The psychogenic contribution to such warming up may be to shift the thermoregulatory set-point" upward (Mrosovsky, 1990). To the extent that stress elevates the thermoregulatory set-point—or simply adds metabolic heat even without raising the thermoregulatory set-point—it should exacerbate what-



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