Nutrition Needs for Mountain Athletes- as science sees it...

Introduction

What’s the most awe-inspiring thing you’ve ever seen? As many incredible things as there are to behold in this big, beautiful world we’re fortunate to live in, I would argue fewer things inspire awe, ambition, and aspiration the way a giant mountain peak with ridges so jagged they resemble the outline of a shark’s mouth more than the granite slabs they are.

Some take this inspiration to an entirely different level by challenging themselves, their bodies, and their safety to pursue athletic endeavors amidst behemoths.

We’ve come a long way in our research of mountain athletes since Boyer and Blume proclaimed, “Little is known about weight loss and changes in body composition at extreme altitudes.” in the 1980s. 1 We’ve grown some in our research over the last 40 years and have come to better understand the demands placed on the body when performing at high altitudes, changes in body composition at these extreme conditions, and overall nutrition needs of mountain athletes.

Pulse on Mountain Athletes: What are the conditions?

In their most general sense, mountain athletes are just that- athletes whose sport, activity, or pursuit takes place in the mountains. These conditions generally mean an environment outside the norm by way of temperature, altitude, muscular demand, increased oxygen demands, etc. Each of these changes either intentionally or unintentionally leads to alterations in an athlete’s nutritional intake while in a high-altitude environment. As you might imagine, changes in intake from baseline can drastically affect an athlete’s weight, lean body mass (LBM) losses, and overall performance. Let’s take a deeper look at what is arguably the biggest nutrition issue with mountain athletes: energy intake.

Predominant Factors Affecting Calorie Intake in Mountain Athletes

There are a variety of factors that affect the overall energy intake of mountain athletes, but all signs seem to point in the same direction: altitude and the type of environment that is often found in the peaks we see dwelling far in the distance.

The following studies do a remarkable job of explaining what happens as a result of reduced energy intake; that is, they explain how much LBM is lost and what percent energy intake reduction is seen in this population- you know the nitty-gritty numbers. As helpful as this objective data is, we chance missing the root of the problem.

Generally speaking, the most common explanation for why people tend to lose so much weight in high altitude environments is rather simple: acute mountain sickness (AMS) or quite simply just known as altitude sickness. AMS can certainly become a much more serious issue that culminates with fluid accumulation in the lungs and/or brain; however, there are documented cases of AMS at the low altitudes of some ski resorts in America. 2 This is relevant to point out because it’s easy to see where a reader’s mind would drift yonder to Nepal and Tibet where the peaks of mountains match the cruising altitude of some jets. This thinking would cause us to miss the larger population of athletes performing ultra-marathons, cross-country ski contests, and climbs here on our own turf in the lower 48.

Without further ado, let’s look at some factors that cause mountain athletes to be in a negative energy balance when it matters most.

Altitude

Author’s note: The literature is full of studies on nutrition and performance “above altitude”. The authors are usually referencing an elevation of around 5000m or of 16,404 feet above sea level; however, when referenced here, I am referring to an altitude of anything above 5,280 feet above sea level unless mentioned otherwise.

I’ve done my best to not bore you with a litany of studies on altitude affecting energy intake, weight loss, loss of LBM, etc., as the findings are much of the same. I have highlighted two that seem particularly relevant and paint a realistic picture of how drastic the effects of elevation can be on energy intake in anyone from trained athletes to weekend warriors.

It’s been well established that energy consumption reduces significantly in high-altitude environments. 3 Some studies have taken it a step further by actually quantifying the reduction in energy intake. Amellini and colleagues set out to evaluate the resting metabolic rate (RMR) and body composition changes in healthy subjects after a 16-day high altitude trekking and climbing expedition. 4 I’d be willing to bet the group would have expected some changes in appetite, energy intake, and RMR; but I’d be curious to know if they expected the type of changes they found.

A 29% reduction in energy intake during high altitude exposure was observed; that’s -1,160kcal deficit on a 4,000kcal die (for those who don’t feel like getting out their old Texas Instruments calculator). The reduction in energy intake caused an average fat mass loss (FML) of 2.2kg and LBM loss of 1.1kg for a grand total of 3.3kg (7.26lbs for those who still haven’t broken out the calculator) over a 16-day period. Now, this is easily enough to make the clinical nutrition professionals among us cry “malnutrition!”, but the fun doesn’t stop there. The loss in FML and LBM caused the estimated RMR at the end of the expedition to be suppressed by 119kcal/day.

It’s not tough to see where an athlete performing several thousand feet above sea level would struggle to eat. There is a combination of factors that contribute to this, but even hormones aren’t immune to the effects of being in an environment that has far less oxygen than what’s found at sea level. Research has shown suppressed levels of ghrelin and leptin in folks at high altitudes. The 2013 study by Shukla et al 5 took a group of people who normally do not live in a high-altitude environment to 11,800 feet above sea level. The group stayed there for 48 hours, had their ghrelin and leptin levels measured, and were then taken up to 14,07 feet above sea level to spend 7 days trekking and climbing. Their results are quite fascinating. They observed a decrease in energy intake of 850kcal/day by the group. The average total weight loss of the group was 2.12 kg at high altitude. Leptin had a significant increase over basal amounts (54.9%!) at the 48-hour, 11,800-foot mark. The levels persisted to be elevated through the seven days and ghrelin decreased by as much as 30% when compared to basal levels. It’s easy to see how the effects of altitude suppress the appetite with these factors are accounted for.

Environment and Temperature

It’s well-known that, on average, temperatures drop significantly as the altitude increases. The question that plagues researchers is, “What does this do to energy intake and balance?”

In one study, a group was given activities to perform in the summer months while a second group was given the same tasks to perform in the winter months. The summer group had a deficit of -924kcal while expending an average of 3937kcal per day. The winter group was found to have a deficit of - 1422kcal when comparing energy intake to energy expended. Both hot and cold extremes produced a greater energy deficit than predicted, but the study results would further suggest that caloric demands are greater in colder environments (i.e. high altitude, cold, mountain conditions) than hot ones. 6

Sure, sure, we could nickel and dime the study limitations by arguing the two groups were different and could have had differing baseline metabolic rates without taking environmental factors into concern whatsoever, but the premise that metabolic demands are higher in temperature extremes remains.

Potential Subjective Factors Affecting Intake

Let’s be honest, it’s not comfortable spending several days in an environment that is cold and lacks oxygen. It hasn’t been well-established what the role of this suffer-fest at high altitude plays in whether or not an athlete eats; however, we have found that when things become a bit more plush and palatable food is offered at 15,000 feet, athletes demonstrate adequate calorie intake and no weight loss. 7

Estimating Energy Needs to Offset Weight Loss

We’ve given it the good ol’ college try when it comes to estimating the needs of these elite athletes via prediction equations. The closest we’ve come was an equation developed by the military a number of years ago (think the 1970s) to estimate how much energy it takes to lug a pack over long distances. 8 It factors in variables like an athlete’s weight, the weight of a pack (considered an essential for many mountain athletes), hiking speed, grade of the incline/mountain (%), and an n-value that is given a numeric factor in an effort to account for the terrain the athlete is treading over; paved roads get an n- value of 1.0, gravel roads a factor of 1.2, and a quad-blasting 3.5 for swamps. 9

Unfortunately, two studies in 2017 determined Mr. Pandolf’s work was actually under predicting the energy needs of folks carrying heavy loads over a variety of less than ideal terrain. 10,11

It’s vital nutrition professionals remember these studies and take each of the aforementioned factors into account when estimating the baseline energy needs of a mountain athlete. It’s also vital we keep in mind these equations are an estimation. They’re a starting point that will likely need adjustment after real-time data can be extrapolated from the athlete; data that aims to answer questions like does the athlete lose, maintain, or gain weight at your original estimation? Does he or she feel like they had enough gas intake to get through whatever event they’ve trained so hard for?

Proposal of a Different Route

There is an array of equations available to measure the resting metabolic needs of a person. All of them have their pros and cons, and if we can all agree on something, it’s the fact that these predictive equations aren’t perfect. It would be wise for nutrition professionals to use a combination of literature and experience to utilize the equation you feel most confident in as a starting point. Once the baseline metabolic demands are established, the remaining needs can be factored in after a dialogue with the athlete establishes what the planned pursuit is, the amount of time involved, and even subjective points like what experience has told the athlete in the past (i.e. “I’ve lost weight eating X calories” on same pursuits in the past). In short, the first calorie recommendation is established through a series of conversations taking place in the months leading up to the event itself. This allows for not only the tweaking of objective numbers, but also the adjustment for what food fills those numbers (i.e. this allows you to create an alternative suggestion if the athlete finds that 15g of honey on a waffle in the morning causes too much GI distress).

Closing Remarks

There’s a variety of circumstances that all merge to create a less than ideal scenario for the human to survive and perform optimally at high altitudes. Anemias, prolonged hypoxia, and other topics that were not touched on in this review also can have profound impacts on an athlete’s performance in the mountains; however, a gross imbalance of energy intake compared to energy needs leading to loss of LBM and reduced performance certainly ranks just as high as those peaks in the distance.

Citations

1. Boyer SJ, Blume FD. Weight loss and changes in body composition at high altitude. Jour of App Physio. 1984 Nov; 57(5): 1580-1585.

2. Honigman B, Theis MK, Koziol-McLain J, Roach R, Yip R, Houston C, et al. Acute Mountain Sickness in a General Tourist Population at Moderate Altitudes. Ann Intern Med. ;118:587–592.

3. P Hannon, G J Klain, D M Sudman, F J Sullivan, Nutritional aspects of high-altitude exposure in women, The American Journal of Clinical Nutrition, Volume 29, Issue 6, June 1976, Pages 604–613. 

4. Amellini F, Zamboni M, Robbi R, et al. The effects of high altitude trekking on body composition and resting metabolic rate. Horm Metab Res, 1997; 29(9): 458-461.

5. Shukla V, Singh S, Vats P, et al. Ghrelin and leptin levels of sojourners and acclimatized lowlanders at high altitude, Nutritional Neuroscience, 8:3, 161-165.

6. Burstein R, Coward A, Askew W, et al. Energy expenditure variations in soldiers performing military activities under cold and hot climate conditions. Mil Med. 1996; 161(12), 750-754.

7. Kayser, B. Nutrition and high altitude exposure. Dept De Physio. 1992; 13, S129-132.

8. Pandolf KB, Givoni B, Goldman RF. Predicting energy expenditure with loads while standing or walking very slowly. 1977 Oct; 43(4): 577-81.

9. Richmond P, Potter A, Santee W. Terrain factors for predicting walking and load carriage energy costs: review and refinement. 2015; 3(3)

10. Bach A, Costello J, Borg D, et al. The Pandolf load carriage equation is a poor predictor of metabolic rate while wearing explosive ordnance disposal protective clothing, Ergonomics, 60:3, 430-438.

11. Drain J, Aisbett B, Lewis M. The Pandolf equation under-predicts the metabolic rate of contemporary military load carriage. Journ of Sci and Med in Sport. 2017 Nov; 20(4): S104- S108.