— Nutrition —
When walking in the mountains, you lose around 350 kcal/hour, to which you must add 100 kcal/hour to combat the cold. For a 7-hour run, the calorie loss is therefore 7 x 450 kcal/hour, i.e. 3150 kcal. To this must be added the loss due to the remaining daily activity, i.e. some 1500 kcal.
Because of the diversity of factors involved, it is difficult to establish the precise calorific requirements of thermoregulation. According to studies by Johnson and Kark, the caloric requirement caused by thermoregulation should be increased or decreased by 5% when the temperature varies by + or – 10 degrees in relation to an average considered to be normal.
The 4650 kcal lost will be made up in the evening or the next day by eating more and richer food. However, it is difficult to exceed a daily intake of 4,000 kcal, so there will be a calorie deficit after 5 to 6 hours of exercise, which will be made up by fat loss.
While it is generally accepted that exercise nutrition should be rich in carbohydrates, the importance of these varies from one specialist to another. In my opinion, the proportion of carbohydrates, lipids and proteins is not the same depending on whether you are doing a one- or two-day race or a race lasting several days at altitude. As a rough guide, we could give the following proportions:
Nutrients |
one week |
2 days |
Carbohydrates |
70% |
55% |
Lipids |
20% |
30% |
Proteins |
10% |
15% |
In addition, it is important to respect the following ratios:
Calories from refined sugars / Total calories < or = 1/10
Animal proteins / Plant proteins > or = 1
Animal fat / Plant fat < or = 3/5
Many books dealing with exercise nutrition offer menus and publish calorie equivalence tables. Reproducing this information would go beyond the scope of this site. All we need to do is give you the following advice.
The day before a race, preferably eat slow carbohydrates in the form of pasta (not overcooked), rice or potatoes.
On the morning of the race, eat some flour (oatmeal, Bircher muesli, wholemeal bread, etc.), cheese and oilseeds (walnuts, almonds, etc.), and above all drink enough.
During the race, eat fast carbohydrates (especially fructose) in the form of dried fruit, fruit pastes, dates, agglomerated tablets, etc., and… drink regularly! When you return from the race, replenish your reserves with fresh meat and vegetables.
But above all, don’t base your menu solely on dietary recommendations, eating according to your own tastes and desires is just as important.