-by Rebecca Dent, High Performance Dietitian
This article includes nutrition tips for expeditions / trips that involve ascent to altitude and provides you with some practical guidance and considerations to help you plan for your trip.
When ascending to altitude, diminished appetite known as hypoxic induced anorexia is experienced the higher you go, with some reporting the effects around 3000-4000m but it is almost certain to occur above 5000m.
With this lack of appetite (leading to a reduction in food intake) combined with an increased metabolic rate and daily physical exertion, weight loss is often experienced. Most of this weight loss that occurs is muscle mass and it is thought that the combination of environmental stress of acclimatizing to altitude and a negative energy balance results in this muscle wastage. This muscle wastage can be further compounded by less active days that are enforced such as poor weather conditions and necessary acclimatization days spent 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 the inability to retain or build muscle mass.
However, 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 this muscle mass loss experienced 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, reduced muscle and as a result, weaker.
The aim is to be as prepared as you can, considering your nutrition requirements before you leave and optimizing your intake during your trip.
Each person’s energy expenditure and nutritional 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 i.e. Trekking, alpinism or mountaineering. Elevation and altitude, gradient and technical requirement to climb, will also impact energy needs and the type of food provisions required. Other considerations include whether the trip is self-supported, whether your load will be carried or if your meals will be cooked and provided for you.
Preparation and planning are key and knowing appetite will be diminished at altitude, it is important to pack foods you find palatable, easy to chew and 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 whilst at home on some of your longer training days out. 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. On expedition during the longer mountaineering days, aim to eat something every 1-2hrs or near to this as practically possible. A rule of thumb to consider is aim to eat 200-300calories every 2hrs. Take snacks that you can stash in easy to reach pockets e.g. shot blocs, gels (e.g. gu), fbombs, gu waffles, PRO bars.
I encourage all of my uphill athlete clients to make a plan of what these snacks will be before they leave for their trip and if possible portion them out into zip lock 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 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 meal times.
To gauge an understanding of what your daily energy requirements may be, research suggests for active individuals performing at altitude, the approx. total daily expenditure equals your basal metabolic rate at sea level times 2.2 – 2.3 (Westerterp et al., 1992). This at least may help give you an idea of where to start when planning your nutrition intake.
Liquids will go down easier if you are struggling with your appetite. Choosing high energy drinks / meal replacements/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: (Additional food examples can also be found in Training for the New Alpinism).
- Home made instant high energy porridge (see my tried and tested recipe below- just add water)
- High energy recovery shake mix
- Salted nuts (cashews, brazils, walnuts, macadamias pack the biggest bang for your buck in terms of calorie content per weight. 100g of macadamia nuts equals a whopping 700calories / 100g, with brazil nuts coming a close second at around 680calories/100g
- Energy gel e.g. GU. Note that the jellied gels (eg Clif Shot Blocks, GU Energy Chews are often easier to eat but are much ‘speedier’ (higher sugar content due to how they have to be made)
- Energy bars that tend not to freeze include, omnibar, tram bars, fourpoints bar, nakd bars, Epic performance bars (generally any bar that is made from pressed dried fruit, nuts and seeds tend to be more resilient against freezing temperatures and wont break your teeth!). Some of these bars also come in a savory flavor
- Sports drink mix or 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 may offset any micronutrient deficiencies
- A Probiotic supplement
- ‘Fat bombs’ – (small sachets of nut butters)
- Oil shots/olive oil to easily add extra calories to meals/freeze dried foods.
- Meal replacement powder (just add water) e.g. British Military expeditions have used Huel, other examples include Feed, Mana, Ambronite.
- Alpine Start instant coffee
- Dried fruits e.g. apricots, dates (apricots and dates both provide a source of iron and vitamin C which are important nutrients at altitude)
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 approx. 800-1000kcal per portion. Price will often denote quality of the ingredients used and taste e.g. LYO Food, Expedition Foods, Good to go, Mountain house, Backpackers 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 intake for each serving and order the sufficient quantity. Again try them before you leave!
High Energy – Oatmeal/Porridge
Mix together –
2 x sachets of instant oats/oat meal
2 tablespoons of desiccated coconut (75calories)
2 tablespoons of whole milk powder (80calories)
1 tablespoons of powdered cream (40calories)
2 teaspoons of dried strawberry powder
1 x fat bomb (200calories)
1 scoop of whey (45calories)
Total Energy = ~650Kcals
This breakfast recipe can be made up before you leave for your trip and stored in individual zip lock bags. Remember test it out before you leave, ingredients can be adjusted to suit your own taste preference.
Hydration and fluid intake is also effected with exposure to altitude. The cold causes diaresis (increase water losses by the body) and also a reduction in voluntary drinking behavior. Read my 10 top tips for hydration here 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 at retaining more fluid. A higher energy drink can help off set significant dehydration and aid rehydrating at the end of a long day.
A side note: If you do suffer from acute mountain sickness (AMS) we know that dehydration and under eating does not cause AMS but significant dehydration and energy deficit can exacerbate symptoms of AMS, making you generally feel worse.
There is a thorough chapter in Training for the New Alpinism on expedition eating and the impact of altitude on our physiology and body composition. It also provides good working examples of how to eat and what to eat when at altitude.
- Training for the New Alpinism
- High Altitude Medicine and Physiology 5th Edition (Text)
- UIAA – The Importance of Nutrition in Mountaineering
- Westerterp, K.R., B. Kayser, F. Brouns, J.P. Herry, and W.H. Saris 1992 Energy expenditure climbing Mt. Everest. J. Appl. Physiol. 73:1815–1819