logistics, and the task at hand. Although a higher fat diet is clearly not a nutritional necessity in the Arctic, it may prove to be a logistical need.
From a metabolic point of view, it is probable that the additional fat calories will be metabolized promptly, to satisfy immediate energy needs, rather than being stored in body fat depots. If extra dietary fat is consumed primarily to meet high daily energy requirements and to prevent weight loss during military operations in cold climates, it will not necessarily have important long-term consequences.
Current national dietary recommendations have been in effect for only a few years, and there is no available research evidence to suggest that a temporary deviation from a low fat diet, eaten in order to meet unusually high energy demands, would have a long-term effect on slowly developing cardiovascular pathology.
If this question is viewed from a risk/benefit perspective, the short-term risks to a soldier who must participate in a dangerous military operation in arctic cold are high, and nutritional assistance must be given to help the soldier function at an optimal level. Clearly, inadequate energy intakes and progressive weight losses are not desirable. The immediate benefits of an adequate energy intake far outweigh the possibility that a short-term intake of extra fat calories (eaten to meet the energy demands of cold, arctic climates) might contribute to deleterious health effects several decades later.
5. What nutrients prevent or lessen the symptoms of acute altitude exposure?
Two nutrients have the reputation of being protective against acute mountain sickness (AMS): water and carbohydrate. Because acute altitude exposure is accompanied by diuresis in most individuals, replacement of water lost through diuresis has been reputed to be important in minimizing the symptoms of mountain sickness. Scientific data on this question are minimal. More careful studies have been done on the effect of carbohydrate feeding during acute exposure to altitude, and the general consensus from those studies is that carbohydrate is of benefit in minimizing the symptoms of acute exposure (Consolazio et al., 1969). Because carbohydrate is the primary metabolic fuel at rest and during exercise (Brooks et al., 1991; Roberts et al., in press a, b), and because it provides slightly more energy for the oxygen consumed than does fat (Kleiber, 1961), provision of ample amounts of this macronutrient could be expected to overcome the 500 kcal/d deficit created by exposure to hypobaric hypoxia, maintain body glycogen stores, and assist in the maintenance of muscle mass.