Metabolism at Altitude : Preventing Acute Mountain Illness through Strategic Nutrition

Last September, my friend and I decided to go camping. We chose an area close to Silverthorne, Colorado (9,035 ft.) and decided to camp above tree line at around 11,000 feet. Both of us were endurance athletes and had done camping trips at altitude many times without complications. We considered ourselves in great shape and ready for any adventure. 

We departed from our home in Fort Collins (5,003 ft.) in the morning and arrived at the trailhead before noon. We were well prepared and had plenty of nutrition in our 40+ lb.-backpacks. The start of the trailhead was at 9,035 ft and we had to hike 7 miles to our destination at 11,000 ft. We were well hydrated, built our camp and went to bed. Both of us had mild edema to our extremities, but nothing that we were worried about as we had experienced these symptoms on multiple hikes to higher elevations in the past. 

We spent the next day hiking above tree line, staying hydrated and fueling with high-quality calories. We have learned from personal experience to eat even when we do not feel like it. We both have experienced weight loss of about 5-10 lbs. per week when camping and hiking above 10,000 ft. 

We did a 7-mile exploratory hike along the ridge line at 11,000 ft. the next day, again, staying hydrated and consuming plenty of calories. We returned to camp when my partner first mentioned a mild pounding headache. He drank more fluids, had dinner and went to bed. 

Rewarding views, in a tent at altitude!

I woke up at around midnight due to my partner running out of the tent. He vomited once and returned to the tent. Something else seemed off. He did not zip the tent door shut when he returned. He mumbled that his head was hurting and kept his head elevated as it relieved the pain to some degree. A few hours later, he vomited again. 

The next morning I proposed that we should pack up camp and hike down the mountain, as he continued to complain of a pounding headache. He refused and wanted to go hike some more. I left the tent site first, walked a few steps and turned around: he was sitting down, staring at the ground. Now I started to really get worried as he was an amazing endurance athlete with a never-ending hunger for adventure. This was not like him. 

I decided to pack up the tent, whether he liked it or not. We needed to get off the mountain before his condition worsened. 

After many attempts, I was finally able to convince him to come with me, and we started our descent. Between 11,000 ft. and 9,000 ft. we walked slow, as his coordination was slightly limited. As soon as we reached 9,000 ft., he started to improve: he started to walk faster, was more coordinated, and communicated more. By the time we got back to our car, he was back to his normal self, however he still had a lingering headache. 

The effects of altitude on his body were very surprising. He demonstrated some classic symptoms of what the high altitude medical community refer to as “HACE”, High Altitude Cerebral Edema: headache, vomiting, confusion, and ataxia (a loss of control of body movement). The experience was unexpected and scary. Cell phone reception is very limited in the backcountry and if his condition would have worsened, this trip could have ended in a very bad situation. 

Summit County, Colorado is a beautiful place to explore the outdoors, hiking and camping. I recently had a conversation with an avid outdoorsman who calls Fort Collins (4,982 ft.) his home and enjoys hiking and camping in Summit County at elevations ranging from 9,000 ft – 12,000 ft. He stated that he consistently experiences unwanted weight reduction of around 5-10 lbs. in body weight per week when living in the backcountry at elevations above 9,000 ft.

Is this weight loss related to increased activity without adjusting calorie intake? Could this weight loss be related to exposure to higher elevation and possible changes in metabolism? How can one keep track of calorie-cost and anticipate the inevitable stress on the body at altitude?

Compare your activity level

A GPS or even a pedometer can help measure and compare activity. An increase in miles or steps compared to baseline may require caloric adjustment in order to prevent weight loss. Calorie input should equal calorie expenditure in order to prevent weight loss. It is important to take into consideration that hiking in the mountains usually requires a high level of physical performance due to elevation gain and loss as well as walking on uneven surfaces which result in increased muscle recruitment.

Increased basal metabolic rate (BMR)

According to Dünnwald et al. (2019), exposure to higher altitude increases BMR initially as the body is adapting to the hypoxic environment. The study concluded that increased sympathetic activity and hypoxia may be responsible for the increase in BMR. Due to more extreme exposure to elements such as cold, wind, rain and snow, involuntary shivering may also contribute to an increase in calorie expenditure and should be considered when preparing for the backcountry.

Decrease in appetite

Another factor contributing to possible weight loss may be related to a lack in appetite. Research on the cause of high altitude anorexia is ongoing, however some researchers believe there may be a correlation between a change in appetite-stimulating hormones at altitude. A study by Shukla et al. (2005) found a decrease in total levels of the appetite-stimulating hormone ghrelin, peptide YY, glucagon-like peptide-1, and leptin at initial exposure to altitude. Pre-packaging and scheduling meals while hiking at altitude may aide in the prevention of weight loss during backcountry activities.

Muscle atrophy

Chaudhary et al. (2012) propose that changes in protein turnover in hypoxic environments may be related to muscle wasting, including a decrease in protein synthesis and an increase in protein degradation. To minimize muscle atrophy, it is important to consume high protein foods frequently. Amino acids may also aide in protein synthesis. Packing snacks with high nutritional value can prevent weight loss. Nutrition labels on food items are a great way to identify optimal snacks.  

Hiking in the backcountry on a multi-day trip requires preparation. I choose high-calorie foods that taste good, are light to pack, and have minimal waste. I make breakfast and dehydrated meals at home and put them into individual bags that only require me to add water. Making your own dehydrated meals allows you to avoid unnecessary additives. I supplement throughout the day with high calorie snacks. If I have room in my pack, I also add what I call “novelty” backcountry foods, such as cheese and wine – it is important to splurge every once in a while, even if you live in a tent. 

Great foods for the back country:

  • Butter or Coconut Oil coffee: many companies make pre-packaged individual coffee. One cup of butter coffee is around 200 calories.
  • Perfect Bars: 1 Bar has around 300 calories and 17 grams of protein. 
  • Pro Bars: 1 Bar has 390 calories, they are light to pack and taste great.
  • Nuts and seeds: easy to pack, great source of healthy fats, calories and protein
  • Jerky: we make our own elk jerky. It is a great snack throughout the day with healthy protein and added salt. 
  • Apples: It is difficult to get fresh fruit in the back country. Apples are easy to pack, last for a long time and allow you to get vitamins and fiber. 
  • Dehydrated fruits and vegetables: great addition to oatmeal in the morning and your dinner at night. Dehydrated fruits and vegetables are easy to make at home, very light to pack, and you can rehydrate them in the backcountry. 
  • Oatmeal with protein powder: we pre-package oatmeal with dehydrated fruit and a scoop of our favorite protein powder in individual bags. Just add water and you have a fantastic-tasting and calorie-rich breakfast. 

Every backcountry excursion should be well planned and it is always better to be over-prepared. It is crucial to be knowledgeable about what foods need to be consumed and when, in order to prevent negative outcomes. Know the distance and elevation changes on your trip, prepare for changes in weather, plan your calories out for every meal on every day, and make a schedule to prevent complications related to nutrition. 

Most importantly: enjoy the beauty of the high-elevation backcountry!

Angi Axmann Grabinger is Nurse Practitioner student at the University of Northern Colorado. Angi’s passion in healthcare involves disease prevention and integrative medicine. If Angi is not studying, working or gardening, you can find her exploring the mountains running or hiking. 

References

Chaudhary, P., Suryakumar, G., Prasad, R., Singh, S.N., Ali, S., Ilavazhagan, G. (2012). 

Chronic hypobaric hypoxia mediated skeletal muscle atrophy: role of ubiquitin–proteasome pathway and calpains. Retrieved from: https://link.springer.com/article/10.1007%2Fs11010-011-1210-x

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. Retrieved from:https://www.frontiersin.org/articles/10.3389/fphys.2019.00430/full

Shukla, V., Singh, S.N., Vats P., Singh, V.K. , Singh, S.B., Banerjee, P.K. (2005).  Ghrelin and 

leptin levels of sojourners and acclimatized lowlanders at high altitude. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/16117183

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