. "6. Energetics and Climate with Emphasis on Heat: A Historical Perspective." Nutritional Needs in Hot Environments: Applications for Military Personnel in Field Operations. Washington, DC: The National Academies Press, 1993.
A finding that has been repeatedly documented is that unacclimatized personnel suffer the consequences when suddenly exposed to stressful environments, whether the environmental stress is heat, cold, or altitude. The psychological and physical stresses associated with combat only complicate the adverse situation. At issue is inadequate acclimatization, which with sudden exposure to heat, not only perpetrates physiological strain but lessens initiative and appetite, which negatively affects nutritional status including water balance. The acclimatization process with exposure to hot environments proceeds rapidly, being virtually complete in the working soldier within 10 days (Adolph, 1947; Buskirk and Bass, 1957; Dill, 1938). During this time, body weight is invariably lost due to undernutrition, but the weight may be subsequently regained in toto or in part. Johnson (1946), in his review, concluded that following acclimatization, dietary require-