This article from Uphill Athlete high-performance dietician Rebecca Dent provides nutrition tips for expeditions that involve ascent to altitude. It includes practical guidance and considerations to help you plan for your trip.

Weight Loss on a High-Altitude Expedition

When you ascend to altitude, diminished appetite (known as hypoxic-induced anorexia) is experienced the higher you go, with some reporting the effects around 3,000–4,000 meters. It is almost certain to occur above 5,000 meters.

Between this lack of appetite, which leads to a reduction in food intake, and increases in metabolic rate and daily physical exertion, weight loss is often experienced. Most of this weight loss that occurs is actually a reduction in muscle mass. It is thought that the combination of the environmental stress of acclimatizing to altitude and a negative energy balance results in this muscle wastage—wastage that can be further compounded by days of reduced activity due to poor weather conditions and/or planned acclimatization time at camp. Your capacity for physical exertion is hampered at altitude and generally results in a lower output of effort. A well-conditioned climber will see a meaningful drop in daily energy expenditure on an expedition compared to his or her typical training load when at home. This results in an inability to retain or build muscle mass.

Should I Add Fat to Compensate?

The concept of gaining body fat to compensate for this weight loss during your expedition at altitude is likely to hinder your physical efforts, not support them. Adding more fat is counterproductive. Fat simply adds a “dead weight” that proves to have no physical or metabolic advantage. It will not prevent the loss of muscle mass at altitude, nor the muscle atrophy that comes with lowered activity. Most climbers come home from extended trips to high altitude with a higher body fat percentage and reduced muscle mass, and as a result are weaker than when they left.

The aim is to be as prepared as you can. Consider your nutrition requirements before you leave and optimize your intake during your trip.

Energy and Nutrition Requirements

Each person’s energy expenditure and nutrition requirements on an expedition will differ depending on the individual (e.g., training and conditioning status, gender, body composition, etc.) and the style of your trip (trekking, alpinism, or mountaineering). Elevation and altitude, gradient, and the technical requirements of the climb will also impact your energy needs and the type of food provisions required. Other considerations include whether the trip is self-supported, if your load will be carried, and if your meals will be cooked and provided for you.

To gauge what your daily energy requirements may be, use this rough calculation: Research suggests for active individuals performing at altitude, the approximate total daily expenditure equals your basal metabolic rate at sea level times 2.2–2.3 (Westerterp et al., 1992). This will at least give you an idea of where to start when planning your nutritional intake.

Expedition Nutrition Strategies

Preparation and planning are key to expedition nutrition, as is knowing that your appetite will be diminished at altitude. It is important to pack foods you find palatable, that are easy to chew, and that you know will go down. Perhaps from prior experience you know what types of food choices work well for you. Test out your expedition food plan while at home on some of your longer training days. Our food preferences and tolerances change during physical exertion at altitude.

With a reduced appetite at altitude comes an increase in satiety, meaning you feel fuller quicker on smaller amounts of food. During the longer mountaineering days of an expedition, aim to eat something every 1–2 hours (or near to this as practically possible). A rule of thumb to consider is to aim to eat 200–300 calories every 2 hours. Take snacks that you can stash in easy-to-reach pockets (e.g., Shot Bloks, gels, FBombs, GU waffles, PROBARs).

Have a Plan

I encourage all of my Uphill Athlete clients to plan out their snacks before they leave for their trip, and if possible portion them out into ziplock bags. You may not meet your plan exactly but at least having a plan will encourage and prompt you to eat rather than just leaving it to chance, especially if you don’t feel hungry.

Increasing caloric intake is difficult at high altitude due to the practical issues of eating and reductions in appetite. When you have more time to eat such as during acclimatization days spent at camp, aim to maximize your energy and nutrient intake by paying particular attention to eating more regularly and eating as well as you can at mealtimes.

Liquids will go down easier if you are struggling with your appetite. High-energy drinks and meal replacement/mass-gainer-style shakes (where you simply add water) will go down easier and still provide you with essential energy and nutrients.

Example Food Items to Pack for an Expedition

Note: Additional food examples can also be found in Training for the New Alpinism.

• Homemade instant high-energy porridge: See my tried-and-tested recipe below (just add water).
• High-energy recovery shake mix
• Salted nuts: Cashews, Brazil nuts, walnuts, and macadamias pack the biggest bang for your buck in terms of calorie content per weight. One hundred grams of macadamia nuts equals a whopping 700 calories, with Brazil nuts coming a close second at around 680 calories/100 grams.
• Energy gels: Note that the jellied gels (e.g., Clif Shot Blocks and GU Energy Chews) are often easier to eat but are much “speedier” due to their higher sugar content (a product of how they are made).
• Energy bars that tend not to freeze: These include Omnibar, Tram Bars, Fourpoints Bars, Nakd Bars, and Epic performance bars. Generally any bar that is made from pressed dried fruit, nuts, and seeds tends to be more resilient against freezing temperatures—and won’t break your teeth! Some of these bars also come in a savory flavor.
• Sports drink mix: If facilities allow, take a flask to make a high-energy hot drink using honey/maple syrup, maltodextrin powder, and a pinch or two of salt, or simply a hot chocolate.
• A daily multivitamin and mineral supplement: This may offset any micronutrient deficiencies.
• A probiotic supplement
• FBombs (or other small sachets of nut butter)
• Oil shots/olive oil: To easily add extra calories to meals/freeze-dried foods.
• Meal replacement powder: Just add water. British military expeditions have used Huel; other examples include Feed, Mana, and Ambronite.
• Alpine Start instant coffee
• Dried fruits: Apricots and dates are both sources of iron and vitamin C, which are important nutrients at altitude.

Expedition Eating Tip

Get used to taking food out of your pocket and drinking with your gloves on.

Freeze-Dried Meals

When it comes to freeze-dried meals, choose high-energy serving sizes of approximately 800–1,000 kcal per portion. Price will often denote quality of the ingredients used and taste. Popular brands include LYO Food, Expedition Foods, Good To-Go, Mountain House, and Backpacker’s Pantry. Most cater to specific dietary requirements such as vegan, gluten free, etc. Freeze-dried meals can come in single or double serving sizes. Make sure you check calorie content for each serving and order a sufficient quantity. Again, try them before you leave!

RECIPE: High-Energy Oatmeal/Porridge

Mix together the following ingredients:

• 2 sachets of instant oats/oatmeal
• 2 tablespoons dried coconut (75 calories)
• 2 tablespoons whole-milk powder (80 calories)
• 1 tablespoon powdered cream (40 calories)
• 2 teaspoons dried strawberry powder
• 1 FBomb or other packet of nut butter (200 calories)
• 1 scoop whey powder (45 calories)

Total Energy = ~650 kcal

This breakfast recipe can be made up before you leave for your trip and stored in individual ziplock bags. Remember to test it out before you leave. Ingredients can be adjusted to suit your taste preferences.

Hydration and Fluid Intake

Hydration and fluid intake is also affected with exposure to altitude. The cold causes diuresis (increased water loss in the body) and also a reduction in voluntary drinking behavior. Read my 10 top tips for hydration if you know you will have a limited weight allowance for fluids you can carry and limited access to fluids during the day. Consuming a higher-energy drink is more effective than just drinking water when it comes to retaining fluid. A higher-energy drink can help offset significant dehydration and aid rehydration at the end of a long day.

A Note on AMS

Although dehydration and undereating do not cause acute mountain sickness (AMS), significant dehydration and energy deficit can exacerbate symptoms of AMS, making you generally feel worse.

-by Rebecca Dent, Uphill Athlete High-Performance Dietitian

As our resident High-Performance Dietitian, Rebecca Dent is available for phone consultations about diet, and she can create a Custom Performance Nutrition Plan for you.

Further Reading

There is a thorough chapter in Training for the New Alpinism on expedition eating and the impact of altitude on physiology and body composition. It also provides good working examples of how and what to eat when at altitude.

• Training for the New Alpinism
• High Altitude Medicine and Physiology, 5th ed.
• UIAA’s “The Importance of Nutrition in Mountaineering”
• Westerterp, K.R., B. Kayser, F. Brouns, J.P. Herry, and W.H. Saris. “Energy expenditure climbing Mt. Everest.” Journal of Applied Physiology 1992 Nov;73(5):1815–1819.