Nutrition planning for a high-altitude expedition is different from planning for training at home. Above 3,000 to 4,000 meters, appetite declines. Above 5,000 meters, hypoxic-induced anorexia is nearly universal. At the same time, metabolic rate and daily energy expenditure increase. The result is a caloric deficit that most climbers do not adequately offset, leading to significant muscle mass loss over the course of the expedition.
This article covers what to expect nutritionally at altitude, how to estimate your energy needs, what to pack, and practical strategies for eating when your appetite is working against you.
Why Do Climbers Lose Muscle Mass at Altitude?
When you ascend to altitude, diminished appetite (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 reduction in food intake and the increases in metabolic rate and daily physical exertion, weight loss is common. Most of this weight loss is a reduction in muscle mass. The combination of the environmental stress of acclimatizing and a negative energy balance drives this muscle wastage—wastage that can be further compounded by days of reduced activity due to poor weather or planned acclimatization time at camp. A well-conditioned climber will see a meaningful drop in daily energy expenditure on an expedition compared to typical training load at home, resulting in an inability to retain or build muscle mass. 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.
Should You Gain Weight Before an Expedition?
No. The concept of gaining body fat to compensate for weight loss at altitude is likely to hinder your physical efforts, not support them. Added fat is dead weight that provides 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.
The aim is to be as well-prepared as you can be. Consider your nutrition requirements before you leave and optimize your intake during your trip.
How Do You Estimate Your Energy Needs at Altitude?
Each person’s energy expenditure on an expedition will differ depending on individual factors (training status, sex, body composition) and the style of the trip (trekking, alpinism, or mountaineering). Elevation, gradient, and the technical requirements of the climb will also impact energy needs, as will whether the trip is self-supported, whether loads are carried, and whether meals are cooked and provided for you.
As a rough calculation: research suggests that for active individuals performing at altitude, approximate total daily energy expenditure equals your basal metabolic rate at sea level multiplied by 2.2 to 2.3 (Westerterp et al., 1992). This at least provides a starting point for planning your nutritional intake.
How Should You Approach Eating During an Expedition?
Preparation and planning are essential, especially knowing that your appetite will be diminished. Pack foods you find palatable, that are easy to chew, and that you know will go down well. If you have prior expedition experience, draw on what worked before. Test your expedition food plan at home on some of your longer training days—food preferences and tolerances change during physical exertion at altitude.
With a reduced appetite at altitude comes an increase in satiety—you feel full faster on smaller amounts of food. During longer mountaineering days, aim to eat something every 1 to 2 hours (or as close to this as practically possible). A useful rule of thumb: aim for 200 to 300 calories every 2 hours. Take snacks that you can stash in easy-to-reach pockets (energy chews, gels, nut butter packets, bars).
Plan your snacks before you leave and portion them into individual bags. You may not hit your plan exactly, but having one will prompt you to eat rather than leaving it to chance—especially when you do not feel hungry.
On acclimatization days spent at camp, aim to maximize your energy and nutrient intake by eating more regularly and as well as possible at mealtimes. If you are struggling with appetite, liquids will go down easier. High-energy drinks and meal replacement or mass-gainer-style shakes (just add water) can still provide essential energy and nutrients.
Practical tip: Get used to taking food out of your pocket and drinking with your gloves on before you leave. Practice this at home on cold-weather training days.
What Should You Pack?
The following list covers proven food items for high-altitude expeditions. Additional examples can be found in Training for the New Alpinism.
Homemade instant high-energy porridge: See the recipe below. Just add water. Prepare individual portions in bags before you leave.
High-energy recovery shake mix: Add water at camp for an easy calorie source when appetite is low.
Salted nuts: Cashews, Brazil nuts, walnuts, and macadamias pack the highest calorie density by weight. 100 grams of macadamia nuts provides roughly 700 calories; Brazil nuts follow at about 680.
Energy gels and chews: Jellied gels (Clif Shot Blocks, GU Energy Chews) are often easier to eat at altitude but are higher in sugar.
Energy bars that resist freezing: Bars made from pressed dried fruit, nuts, and seeds tend to be more resilient in cold temperatures. Look for bars in savory flavors as well as sweet.
Sports drink mix: If you have the facilities, make a high-energy hot drink from honey or maple syrup, maltodextrin powder, and a pinch of salt. Hot chocolate also works.
Nut butter packets: Easy to eat, calorie-dense, and don’t require preparation.
Olive oil: To add extra calories to meals and freeze-dried foods.
Meal replacement powder: Just add water. Useful when solid food is unappealing.
Dried fruits: Apricots and dates are sources of iron and vitamin C, both important at altitude.
Daily multivitamin and mineral supplement: May offset micronutrient deficiencies when food variety is limited.
Probiotic supplement: Supports gut function during travel and altitude exposure.
Instant coffee: Morale matters.
How Do You Choose Freeze-Dried Meals?
Choose serving sizes of approximately 800 to 1,000 calories per portion. Price generally reflects ingredient quality and taste. Most brands cater to specific dietary requirements (vegan, gluten-free, etc.). Freeze-dried meals come in single or double serving sizes—check the calorie content per serving and order sufficient quantity. As with everything else: try them before you leave.
[TK: Consider whether to retain specific brand names (LYO Food, Expedition Foods, Good To-Go, Mountain House, Backpacker’s Pantry) or generalize. Brand landscape may have changed since original publication.] (Steve would like to generalize)
Recipe: High-Energy Expedition Porridge (~650 kcal)
Mix together the following ingredients. Prepare individual portions in bags before your trip. Just add hot water.
2 packets instant oats
2 tablespoons dried coconut (75 kcal)
2 tablespoons whole-milk powder (80 kcal)
1 tablespoon powdered cream (40 kcal)
2 teaspoons dried strawberry powder
1 packet nut butter (200 kcal)
1 scoop whey protein powder (45 kcal)
Adjust ingredients to suit your taste. Test before you leave.
How Does Altitude Affect Hydration?
Hydration is affected by altitude exposure in two ways: cold causes diuresis (increased water loss), and voluntary drinking behavior decreases. Consuming a higher-energy drink is more effective than water alone for retaining fluid. A higher-energy drink can also help offset significant dehydration and aid rehydration at the end of a long day.
[TK: Link to Rebecca’s 10 top tips for hydration article if still current]
A note on acute mountain sickness: dehydration and undereating do not cause AMS, but significant dehydration and energy deficit can exacerbate symptoms, making you feel worse than the altitude alone would explain. Staying on top of your nutrition and hydration will not prevent AMS, but falling behind on them will make everything harder.
[TK: CTA — link to Nutrition Coaching page. “As our in-house High-Performance Dietitian, Rebecca Dent is available for phone consultations and can create a Custom Performance Nutrition Plan for your expedition.” Also link to Training for the New Alpinism for the full expedition nutrition chapter.]
Further Reading
Training for the New Alpinism — includes a thorough chapter on expedition eating and the impact of altitude on physiology and body composition.
High Altitude Medicine and Physiology, 5th ed.
UIAA, “The Importance of Nutrition in Mountaineering”Westerterp, K.R., et al. “Energy expenditure climbing Mt. Everest.” Journal of Applied Physiology 1992 Nov;73(5):1815–1819.