Nutrition Considerations When Training in Different Environments
Whether you are living somewhere with dramatic season changes, or if you take part in events in harsh environments (extreme temps and/ or at high elevation), nutrition considerations should be made when planning your fueling strategies. Exercising in extreme environments can influence your metabolic rate, substrate utilization and rate of fluid loss.
Hot Climates
One of the adaptations made to improve thermoregulation in hot climates is increased sweat production. Sweat rates are higher when exercising in hot vs. temperate or cold climates. Hot and dry climates lead to more sweat production compared to hot and humid climates. This can mislead athletes into thinking they are sweating less than they actually are. Higher sweat rates pose more concern for dehydration and mineral loss. Sodium is lost in the highest amount through sweat, and to a lesser extent, the electrolytes potassium, calcium and magnesium. In addition to these electrolytes, the minerals iron copper and zinc are lost, however, excessive losses usually do not occur since they are preserved (less lost through sweat) as part of the acclimation to heat process.
Exercising under heat stress (either in dry or humid climates), there is an alteration in substrate use. An Increase in glucose (carbohydrate) utilization occurs; there is both an increase in intramuscular glycogen use and glycolysis. Simultaneously, fat utilisation decreases when exercising with heat stress. Additionally, there is some evidence to suggest that there may be an increase in protein utilization as fuel.
When you exercise in hot climates, it would be wise to carry adequate volumes of a carbohydrate-containing sports beverage with you. These beverages encourage drinking due to their flavor, which may mitigate or prevent dehydration. The sodium/ electrolytes they contain replenishes losses, and aids in fluid retention. The carbohydrates from the sports drinks will be important to slow down the glycogen depletion that may otherwise occur more rapidly from carbohydrates increased use as fuel.
Post event, be sure to include carbohydrate rich foods- whole grains, starchy vegetables, fruits, etc and at least 20 grams of protein to replenish the muscle proteins that were broken down for fuel.
Cold Weather
Cold temperatures increase your resting metabolic rate by ~3-7%, meaning you will be burning more fuel for energy. This includes both seasonal changes and when traveling from warm to cold climates. A substantial amount of fluid loss can also occur with exercise in cold climates.
Hydration and fueling during very cold temperatures has other, unique challenges. For instance, hydration tubes freezing, some foods may become too frozen to eat with ease (e.g. a rock hard/ frozen Cliff bar is a lot harder to chomp on). Additionally, if refueling requires removing gloves or stopping temporarily, many athletes may be tempted to skip or cut back on fueling. This could result in dehydration and/ or underfueling- both negatively impact performance.
When you exercise in cold climates, plan your hydration and fueling strategy accordingly by choosing easy to access food and/or fluid. Make sure what and how you pack items will make them convenient to consume. If you are experienced with running in cold temps, you probably have these strategies dialed.
High Altitude
High altitude is generally considered 10,000 ft (3048 m) above sea level. When exercising in high altitude environments, there is a slight change in substrate utilization, shifting to an increase in anaerobic glycolysis. In other words, you are using more carbohydrates (glucose, glycogen) as fuel, with concurrent decreases in fatty acid oxidation. This shift is similar to what happens when exercising in hot climates (discussed above). Additionally, reaching high altitude will increase your resting metabolic rate, as happens with exposure to cold weather, and to a larger degree of 15-25%! However, this increase in metabolism is temporary and will return to your baseline after 1-3 weeks as part of the acclimatization process. As seen with exercising in hot climates, high altitude may cause more protein to get used for fuel (not a desirable alteration).
With the combination of an increased metabolic rate and higher carbohydrate use, you will deplete your carbohydrate stores more rapidly, if adequate carbohydrates are not consumed. Aim to have 30-90 grams carbohydrate/ hour - depending on your tolerance and duration you will be exercising (see carbohydrate page for more information of carb needs). Consuming a carbohydrate-containing sports drink is one good option for getting more carbohydrates during your run.
Post exercise fueling will be important for replacing any accrued deficits (fluids, electrolytes, glycogen, calories, protein, etc). Be sure to include plenty of carbohydrate rich foods and at least 20 grams of protein to replenish muscle glycogen and proteins.
References
Febbraio, M.A. Alterations in Energy Metabolism During Exercise and Heat Stress. Sports Med 31, 47–59 (2001). https://doi-org.ezproxy.lib.utah.edu/10.2165/00007256-200131010-00004
Dunford M & Doyle JA. Nutrition for Sport and Exercise 4th ed. Cengage. 2019.