intake, less weight loss, and improved customer satisfaction. These studies will also be reviewed from the perspective of trying to develop a better understanding of the factors that control food intake during military exercises.
The Meal, Ready-to-Eat (MRE) was introduced as the military's operational ration in the early 1980s. Packaged in a flexible, retort pouch2, it replaced a canned ration, the Meal, Combat Individual (MCI). Components of both rations can be eaten hot or cold and provide a nutritionally complete diet. When the MRE was introduced into the military feeding system, there was considerable interest among military planners and logisticians in having troops subsist on operational rations as their sole source of food for lengthy periods of time. For this reason the initial test of the MRE was designed to determine the consequences of prolonged feeding of this ration to troops during an extended field training exercise (Hirsch et al., 1985).
During MRE test development, the remaining stock of MCIs was being depleted, and some units were already eating the MRE in the field. Undocumented reports from these units suggested that troops consuming the MRE were experiencing gastrointestinal difficulties. These rumors, in conjunction with the possibility that food monotony (Kamen and Peryam, 1961; Schutz and Pilgrim, 1958; Siegel and Pilgrim, 1958) might develop with the MRE, led to the decision to conduct a laboratory test prior to a field evaluation (Hirsch and Kramer, 1993). The Army was concerned that a serious decline in consumption might occur when a ration with as few different components as the MRE was fed as the sole source of food for an extended time.
The results of two extended feeding studies where the MRE was fed as the only source of food (Hirsch and Kramer, 1993; Hirsch et al., 1985) provide both a definition of the underconsumption problem and potential insight into its solution. The laboratory study was conducted with paid student volunteers at the Massachusetts Institute of Technology over a 44-d period (Hirsch and Kramer, 1993). Volunteers took all their meals in a small, pleasant dining room. Hot and cold water was available for preparing beverages and