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protein consumption. As a result of the organoleptic changes in fat within foods in conditions of extreme heat, however, food products that contain significant amounts of fat may be deemed unacceptable by soldiers and thus may not be consumed.

The requirement for sustained physical activity in hot environments might result in the need for a modified ration that would encourage food consumption, for example, one lower in fat and higher in carbohydrate that could be consumed with little preparation. Heat-stable food products that are similar to those available in the private sector appear to be preferred by soldiers in terms of appetite. In designing MRE rations for use in hot environments, information from the experience gained during Operations Desert Shield and Desert Storm should be combined with what is known about how food preferences change in the heat. Moreover, factors other than ration composition that may influence food intake need to be considered. These include the availability of potable liquids in generous supply, the eating situation of troops (i.e., alone or in groups), the time of day when food may be offered, and the convenience of consuming the rations. Nonnutritional factors such as these can have a significant influence on ration intake.

  1. What factors may influence food intake in hot environments?

The major factors that appear to influence food intake in hot environments are the need to maintain body temperature (through decreased intake to reduce the thermic effect of food) and the apparent relationship between decreased body weight and decreased body temperature. With the hydration regimens in place in the military, which appear to encourage adequate fluid intake, and the awareness among military personnel of potential heat stroke, the observation in laboratory animals of markedly decreased food intake to prevent hyperthermia is probably not a significant concern within the military population.

Other factors such as psychological stress may further depress food intake. In addition, the lack of a desire in hot environments to eat hot foods (even though their palatability may be greater than that of cold foods) and the concomitant increased desire to consume cold foods are documented somewhat subjectively in nationwide surveys of food intake of individuals from households in the U.S. general population during various seasons. The intake of food by humans in a hot environment may be further influenced by the availability of cool potable water, the time of day, the psychosocial environment, and ration components.

  1. To what extent does fluid intake influence food intake?

Animal studies demonstrate that dehydration markedly decreases voluntary food intake and that forcing foods during dehydration results in increased mortality. Although there have been a few human studies of this



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