Altitude camps are widely used by elite athletes because hypoxia produces physiological benefits, including natural stimulation of erythropoietin and increased red-blood-cell production. Many competitions also take place at altitude, particularly in trail running and cycling, so spending several weeks training in those conditions can help athletes adapt.
Several factors must be considered before planning an altitude camp, and nutrition plays a fundamental role.
Effects of altitude on metabolism
As discussed in previous posts, atmospheric pressure falls at altitude, reducing the amount of oxygen we can inhale. Maximal oxygen uptake (VO2max) and physical performance consequently decline. VO2max is estimated to fall by an average of 6.3% per 1000 meters above sea level, while performance in an incremental test may fall by as much as 14.5% per 1000 meters (Wehrlin & Hallén, 2006). The same activity therefore requires more effort and oxygen at altitude, making us less efficient. This is evident even at complete rest. One study in 10 highly trained athletes found that resting metabolic expenditure increased by 19% during an altitude stay at 2200 meters above sea level lasting 4 weeks (Figure 1), yet the athletes did not increase energy intake (Woods et al., 2017).
The risks of increased metabolism
Higher energy expenditure at altitude, both at rest and during exercise, can have negative consequences unless energy intake rises accordingly. The opposite commonly occurs. A recent study of 17 participants who climbed to 4300 meters for 22 days found that appetite decreased at altitude, particularly during the first few days, because insulin and leptin levels rose and inhibited signals that promote food intake (Karl et al., 2018).
The resulting energy deficit may not only prevent the expected benefits of altitude exposure but also cause harmful adaptations. A recent study (Berryman et al., 2018) found that a 40% calorie deficit during a stay at 4300 meters lasting 22 days could produce around 8 kilograms of weight loss, including 3.6 kilograms of muscle, regardless of whether participants consumed 1 or 2 g/kg of protein per day. A recent meta-analysis likewise confirmed that altitude stays are generally associated with significant losses of body weight (2.6 kg), fat mass (1.5 kg) and fat-free mass (1.3 kg). These changes increased with altitude, including an average loss of 4.9 kg during stays at extreme altitudes of >5300 meters (Dünnwald, Gatterer, Faulhaber, Arvandi, & Schobersberger, 2019).
Conclusions
At altitude, the energy cost of every activity—including resting metabolism—increases, yet energy intake tends to decrease. This deficit can have important consequences and is associated with loss of body weight, including substantial muscle loss. Increasing protein intake may help during altitude stays, but minimizing the energy deficit by consuming more calories throughout the day is the primary priority.
AUTHOR
Pedro Valenzuela
Researcher in the Physiology Unit at the University of Alcalá and the Performance Monitoring Unit at the Sports Medicine Center (AEPSAD, Madrid High Performance Center).
Website: www.fissac.com
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References
- Berryman, C. E., Young, A. J., Karl, J. P., Kenefick, R. W., Margolis, L. M., Cole, R. E., … Pasiakos, S. M. (2018). Severe negative energy balance during 21 d at high altitude decreases fat-free mass regardless of dietary protein intake: A randomized controlled trial. FASEB Journal, 32(2), 894–905. https://doi.org/10.1096/fj.201700915R
- Dünnwald, T., Gatterer, H., Faulhaber, M., Arvandi, M., & Schobersberger, W. (2019). Body composition and body weight changes at different altitude levels: A systematic review and meta-analysis. Frontiers in Physiology, 10(MAR). https://doi.org/10.3389/fphys.2019.00430
- Karl, J. P., Cole, R. E., Berryman, C. E., Finlayson, G., Radcliffe, P. N., Kominsky, M. T., … Pasiakos, S. M. (2018). Appetite Suppression and Altered Food Preferences Coincide with Changes in Appetite-Mediating Hormones during Energy Deficit at High Altitude, but Are Not Affected by Protein Intake. High Altitude Medicine and Biology, 19(2), 156–169. https://doi.org/10.1089/ham.2017.0155
- Wehrlin, J. P., & Hallén, J. (2006). Linear decrease in VO2max and performance with increasing altitude in endurance athletes. European Journal of Applied Physiology, 96(4), 404–412. https://doi.org/10.1007/s00421-005-0081-9
- Woods, A., Sharma, A., Garvican-Lewis, L. A., Saunders, P., Rice, T., & Thompson, K. (2017). Four Weeks of Classical Altitude Training Increases Resting Metabolic Rate in Highly Trained Middle-Distance Runners. International Journal of Sport Nutrition and Exercise Metabolism, 27(1), 83–90.
