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Key tips on how to adjust your diet in extreme conditions such as high altitudes, hot or cold weather.

This article is presented by the Swiss Sports Nutrition Society

Right now, everyone is talking about sport in extreme environmental conditions. The past Winter Olympic Games in Beijing took place in extreme conditions, just like the Summer Olympic Games in Tokyo. Whereas the athletes in Beijing had to contend with strong winds and icy temperatures as low as minus 25 degrees, the extreme heat and humidity levels in Tokyo were no less difficult. However, with good planning in terms of clothing, training and nutrition, our bodies can also perform incredibly well under these circumstances. 

Nutrition in high altitudes 

At high altitudes, the barometric pressure drops, thus reducing the availability of oxygen. At the same time, the need for fluid intake increases due to the usually dry and cold air and faster respiratory rate, for example. This increased fluid loss can lead to symptoms such as headaches. It is therefore advisable to drink plenty of fluids throughout the day. 

At high altitudes, resting energy expenditure also increases while appetite regulation is simultaneously suppressed. As a result, you may be inclined to not consume enough energy. This can lead to limited training adaptations and unwanted weight loss. Especially when you consider that your training volume is usually higher at high-altitude training camps, and therefore your energy requirement is already greater than at home. 

Due to the loss of appetite at high altitudes (> 3000 m), eating foods with an extremely high energy density or fat content has proven to be helpful. Particularly for mountaineers, where the energy to weight ratio seems to be ideal (e.g. nuts, chocolate, etc.). 

Athletes who travel to high-altitude training camps with low iron stores can develop an iron deficiency relatively quickly. It is therefore advisable to check your iron storage level 4-10 weeks before you depart in order to rectify any deficiencies before residing at high altitudes. 

Nutrition in the heat 

Extremely hot and humid environmental conditions can increase not only the physiological but also psychological stress related to the sporting load. Countless publications have shown that there is a loss in performance capability in the heat. Fluid balance is one of the most studied and important topics pertaining to nutrition in the heat (and high humidity). Because it is difficult to establish general drinking recommendations, the sweat rate (see the hydration calculator) and salt loss during physical exertion are measured. The measured data can then be used to establish individual recommendations with regards to drinking behaviour.
 
Your carbohydrate metabolism also speeds up under the influence of heat and your lipid metabolism slows down. However, current recommendations on the intake of carbohydrates are still based on the duration and intensity of the physical exertion and less on environmental conditions. 

Incidentally, gastrointestinal problems can also occur more frequently when training in the heat. A good nutrition, drinking and cooling strategy is therefore of central importance. 

Nutrition in the cold 

Spending time in cold conditions can impact the performance of our respiratory system. Frostbite and hypothermia are also common symptoms. Above all, athletes with a low body fat percentage, low muscle mass, or limited carbohydrate stores in the muscles seem more likely to suffer from hypothermia. 

Winter athletes naturally try to counteract these conditions by wearing the appropriate clothing. Excessive sweating and wet clothing that doesn’t dry can also quickly lead to hypothermia. In cold weather, it is therefore important to maintain your fluid balance and to counteract any reduction in your hydration level. 

Even your resting energy requirement can increase under extremely cold conditions. This increased energy requirement is attributed not only to excessive heat production but also to the increased consumption of carbohydrates. If your energy supply is inadequate, this can impair your heat production and thus trigger hypothermia. It is therefore advisable to increase your fluid and carbohydrate intake in relation to your normal everyday conditions. Consuming warm food or drinks can also help to warm your body and make you feel better.

Conclusion 

Regardless of whether you're facing high altitudes, or hot or cold weather, it's advisable to deal with the prevailing extreme environmental conditions first and draw up the right plan. This is the only way to ensure your body is ideally accustomed to the new conditions, so you can attain the optimal training stimulus or maximum performance under difficult conditions.