thermoregulation and maintenance hydration, but it encompasses psychological stress as well. It is difficult to ascertain the difference between appetite and hunger in animals; in humans, however, for whom other factors, such as situational stress, may affect hunger and appetite differently, it may be important to differentiate the two. Both, singly or in combination, will affect food intake. Given the stress expected with military excursions into hot and tropical environments and the rapid deployment that troops often experience, any evaluation of food intake and habits in hot environments should include all possible stressors to determine the potential combined effects of these factors.
In studies to determine the preferred types of foods for consumption in hot environments, palatability per se has not been measured in hot versus cold environments. In temperate environments, studies show that humans have an expressed preference for fats and sweets (Drewnowski et al., 1989). There is currently a dearth of solid experimental research on human food consumption in response to variations in heat. In terms of the proportions of various macronutrients in the diet, protein as a percentage of energy remained constant in military nutrition studies conducted during different seasons over the course of World War II (Edholm et al., 1964; Johnson and Kark, 1947). These data were supported by animal studies (Donhoffer and Vonotzky, 1947). Rolls and others (1990), however, found almost no relation between how hungry or satiated people claimed to be and how much they subsequently ate.
One classic study in food intake changes among military personnel was conducted by Edholm and Goldsmith (1966). Two similar groups of military men were followed in carefully controlled conditions. One group had spent a year in Bahrain prior to the experiment; the second group was first studied for 12 days in the United Kingdom and then flown to Bahrain, where it joined the first group. Both groups of subjects spent the first 4 days engaged in hard work, the next 4 days engaged in lighter work, and the final 4 days engaged in hard work in tents and outside. Both groups then returned to the United Kingdom for a repeat of the 12-day protocol.
In Bahrain the daytime temperature rarely went below 30°C (86°F), with a relative humidity of 40 to 90 percent. The mean food intake in Bahrain was approximately 25 percent less than that in the United Kingdom; however, the percentages of calories from fat and carbohydrate were similar, as was the percentage of calories from protein. While in Bahrain, the unacclimatized group lost an average body weight of 2.5 kg over 12 days, and the acclimatized group lost 1.1 kg. The lost weight was not quickly recovered upon the groups' return to the United Kingdom. This result led