Article by Ruth McKean, Sports Nutritionist

2. Energy Requirements at High Altitude


Total energy requirement is the absolute amount of energy that is required to maintain energy balance. You neither lose nor gain weight, as total energy intake = total energy expenditure.

At altitudes greater than 2500m one of the most common observations is weight loss reported to be due to a reduced appetite and in turn a reduced energy intake, and an increase in basal metabolic rate. Several studies have showed that the energy intake to maintain body weight at high altitude in moderately active individuals is significantly higher than that required at sea level.

In a study of a military expedition to the Bolivian Andes (5600m) it was shown that after 18 days, when the subjects had acclimatised, all had lost weight (mean weight loss 4.35kg, SD 1.60). Weight loss over a short period of time may be acceptable but losses sustained over a longer period would give cause for concern due to a loss of muscle. Some of the subjects reported deliberately gaining weight prior to departure. However, if food is readily available during your stay at altitude increasing body weight before ascent will not protect against muscle wasting and weight loss. The subjects also reported feeling fuller and considered there to be too much to eat at altitude yet subjects were issued with the same military arctic ration packs which they had been given at sea level leading up to the expedition in the Andes. The arctic packs consisted of porridge, chocolate drinks, instant soups, potato powder, sugared tea and coffee, mint cakes, biscuits including fruit biscuits, nuts and raisins, sugar tablets, and some milk chocolate. These are all energy dense foods.

In view of the above study and many others, it is now the general consensus that your total energy intake at high altitude should be higher than sea level, despite a possible lack of appetite.

To overcome this lack of appetite it is recommended that you plan your daily food intake if you are going to be at altitude for a prolonged period. For example, agree to consume a set amount of food that would meet your sea level requirements and some extra food to cover the increased energy needs of altitude as well as the possible increases in energy requirements due to harder terrain, loads carried and the level and type of activity. It has been estimated that for men an additional energy intake of 1050-1260Kj (252-303kcal) per day and women 756-840kJ (182-202kcal) per day is required to maintain an energy balance whilst at rest.

Now that it is established that energy needs are increased at altitude the next question is what type of energy should you predominantly be consuming - Fat, carbohydrate or protein?

 

 

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