consistent problem. Typically, soldiers did not consume sufficient calories to meet energy expenditure and consequently lost body weight. The energy deficit has been in the range of 700 to 1,000 kcal/d and thus raises concern about the influence of such a deficit on physical and cognitive performance, particularly over a period of extended use. Anecdotal reports from Operation Desert Storm, for example, indicated that some units may have used MREs as their sole source of food for 50 to 60 days—far longer than the original intent when the MRE was initially field tested. In contrast, studies with special purpose subsistence rations that supplied limited energy (1,500–2,000 kcal), but were based on similar design of the MRE, reported that the rations were fully consumed, and soldier weight losses were experienced as would be predicted by the limited calories in the rations. Systematic records of personnel weight loss and nutritional status were not maintained during the combat situation of Desert Storm. There were, however, no apparent major nutritional problems associated with this long-term use of MREs. Based on continuing research with the MREs as described later in this chapter and in Chapters 6 through 10 of this report, the Army Surgeon General, with concurrence from the Air Force, Marine Corps, and Navy, has recently issued a revised policy statement that ''…allows the MREs to be consumed as the sole source of subsistence for up to twenty-one days" (U.S. Department of the Army, 1995).
There have been successive modifications of the MRE since 1981. These modifications in type of food items, diversity of meals, packaging, and food quality have produced small improvements in total consumption but have not significantly reduced the energy deficit that occurs when MREs are consumed. This problem continues in spite of positive hedonic ratings of the MRE ration items in laboratory and field tests. The suboptimal intake of operational rations thus remains a major issue that needs to be evaluated.
This report originated from a concern within the military about the consistency of the deficit in energy intake and whether such a decrement could lead to meaningful reductions in physical and/or cognitive performance of troops during military operations. The report focuses on the various factors that may contribute to the reduced intake of operational rations, the potential effect on soldier performance, and suggested steps that may be taken to overcome the problem. The data covered in this report are limited to controlled field studies of operational rations. The information and conclusions drawn from these data, while reflecting the military performance demands in rigorous field conditions and environmental extremes, do not, however, reflect the extreme physical, social, and psychological stress of combat.
The CMNR of the Food and Nutrition Board (FNB), Institute of Medicine, National Academy of Sciences, was asked to assist in a collaborative program