Nutritional Considerations for Cold Weather Hiking

By Brenda Braaten
Reproduced from BackPackingLight.com, 2003

The article describes an American experience: some aspects are not recommended in Australian conditions
Notes in [] have been inserted by the maintainer and are his responsibility.
Send any other comments to the maintainer Roger Caffin

Introduction

As I stood in the frigid cold stomping my feet in the snow, watching my husband hastily putting up the tent in the fading light, I admitted defeat. Three separate attempts on Mt. Whiteface (a relatively insignificant 4,000-footer in the White Mountains) and three times defeated by weather. Leaving home, we had optimistically calculated a same-day return. Before we had traveled a mile up the trail, however, we realized that it was a good thing we had packed food and gear for two days. Snow that had just been dusting the lowlands quickly turned to snowdrifts as we ascended. We were soon post-holing up to our knees, castigating ourselves for leaving our snowshoes in the warmth of our basement one hundred miles away. Following in the footsteps of my husband, I had it fairly easy, but by 4 pm I was exhausted and grateful to see the sun setting, knowing that fading light would be the catalyst for setting up camp for the night. Our destination nowhere in sight, we had to rethink the itinerary.

The tent ready, my husband turned eagerly and asked where I wanted to set up the kitchen. I snapped back: "No Food! I'm too cold. I can't eat." as I dove into the tent and the insulating layers of sleeping bag and liner. Concerned for my well-being (and perhaps a bit hungry himself), he soon had the stove humming and fixed dinner as I dozed off. "Here, drink this, you're dehydrated," he admonished as he handed hot soup into the tent. It hurts to say it, but he was absolutely right. I hadn't reckoned how quickly the extreme hiking effort (ascending and post-holing) and the dry cold air would sap the moisture from my pores and from my breath. I had not replenished my losses, repeatedly rejecting his offers of a sip from his water bottle. The dehydration had turned to nausea at the thought of dinner. It was not the cold that was defeating me - it was my own stupidity. What had I learned from this day's journey? [Note 5]

Snack Often!

First, recognize that when hiking in extreme cold (below 10 F), you will be burning an additional 250-500 Calories/day ¹. [Also Note 4] Your body will be running the furnace at full blast to keep your core temperature within reasonable limits, but the layers you are wearing should protect you from using excessive Calories to keep warm. The real Calorie burner is the extra effort it takes to move more gear over worse terrain. Even relatively level terrain is more challenging if you are post-holing into knee-deep snow at every step. It takes twice as many Calories to walk in soft packed snow as it does to walk the same distance on cleared trails (Askew et al., 1989).

Getting more fuel when weather is extremely cold becomes a challenge, since slowing down for a three course lunch means a drop in body temperature with resulting cold fingers and toes. Thus, "grazing" should be the meal pattern: small, frequent snacks throughout the day to most effectively fuel your muscles. To adapt your normal warm weather menu, plan to add 4-8 extra servings of high carbohydrate/high fat snacks per day, with lunch reduced to the status of a "large snack". Plan to nibble along the trail, as hands and feet will freeze up quickly if you stop for a mac 'n cheese delay.

Put on extra layers before you need them, as soon as you slow down, to avoid long moments of uncomfortably cold extremities later on. To avoid robbing your arms and legs of necessary circulation, eat small meals, rather than large meals that shunt blood to the intestine. Timing your meals will also make a difference in how you feel. Eating dinner or a hearty snack just before you go to sleep (500-1200 Calories) will help you sleep warmer and more soundly.

BPL Editor's Comment: One of our reviewers adds, and Dr. Braaten agrees, that "…these calories should include a high proportion of fats, which can be utilized more efficiently, and a significant portion of protein, needed to restore muscular endurance for the following days' activities, should be included in that amount."

Sip Often!

Stay hydrated. Dehydration compounds the effects of cold weather exertion, causing more physical strain on heart and skeletal muscles, leading to earlier exhaustion. Avoid dehydration by sipping water often throughout the day. To keep water bottles from freezing, pack them inside your jacket next to your body, sleep with them in your sleeping bag (along with your boots--in a plastic bag of course), and buy/make an insulated bottle jacket. Two partially full bottles will freeze faster than one full bottle, so combine the water bottles if you have two that are less than half full. Adding gatorade/Kool-Aid will depress the freezing point, keeping it liquid longer, but at less than 10 F even sugar water will freeze. Fluids that contain too much sugar will promote diuresis (you lose more water than you gain), so a 7% solution, or approximately 1/3 C powder per liter, is recommended to maintain optimum hydration status (Rintamaki et al., 1995).

Foods to Avoid

Avoid any food that makes you "think you're hot when you're not". Foods that cause you to break out in a sweat--alcohol or spicy foods containing hot peppers, for example. Even too much hot fluid at once can cause vasodilation, allowing precious warmth to escape from your pores. Water/fluid should be about body temperature, or taken in small sips if very hot (Rintamaki et al., 1995). Avoid high protein snacks, as they increase your water requirement and reduce your cold tolerance. 10% to 15% Calories from protein is generally adequate (Stroud et al., 1996). [See Note 6]

Prepare in Advance

Be mindful of the effect subzero temperature will have on your food rations. What are you going to do with 5 bagels that have frozen solid on your high country/mid-winter trip? Use them for hockey pucks? Take chips or cheese crackers instead. Generally, the less water in any food, the better. The lower water content makes them less likely to freeze solid. Pack dehydrated soup and instant cereal mixes, Summit bars or granola bars--foods that require little or no preparation and that contain no water. (See www.frc.mass.edu/bbraate/packlite/index.htm for Water Content of Common Trail Foods.) Do as much of the food preparation as possible in the warmth of your kitchen: slice sausage/Kielbasa and cheese, package food in baggies so that all you have to do is heat water to a boil and dump the contents in. No stirring required; no frozen fingers. I even remove tea bags from their wrapper. Think through every step of food preparation that will be required on the trail as though you had to do it with mittens on, and simplify accordingly. [See Note 6]

Take Extra Fuel

Beside needing more fuel yourself, you'll need at least 3 times more stove fuel to melt snow and heat it to boiling (not correcting for additional environmental losses due to conductance, exposure to wind, etc.). Everything will take longer--take plenty of fuel (see Note 2). [Also see Note 3]

When melting snow, be aware that you should start with some liquid water in your kettle, otherwise your pan will scorch and the water will taste burned. (Editor's Note: some water in the kettle will also improve the heat transfer efficiency among the water phases in the pot and promote faster melting time. But 'burned' is rather ridiculous.)

Because there were teenagers awaiting our attention at home, we returned to the valley the next morning. We had not conquered Mt. Whiteface this trip, but it was not the cold that defeated us. Rather, because the cold had discouraged the masses, we had been graciously provided with what we needed most: profound solitude, spirit-renewing perspective. Undaunted, we could eagerly anticipate "the next time", better educated than when we began this trip. Next time, I'll bring the snowshoes, and yes, I'll drink my water throughout the day.

Key Points to Remember

Sip water/fluids throughout the day.
Take at least three times more fuel than you would for summer hiking. [Note 3]
Avoid a high protein diet. Eat frequent high carbohydrate/high fat snacks.
Have a substantial snack just before bedtime (high protein OK here).
Pack no-fuss meals: instant hot soups or cereals, hot drinks.
Do the prep work at home: wash veggies/fruit, slice cheese/sausage in the warmth of your kitchen.
Pack dehydrated/low moisture foods.

End Notes

BPL Editor: One of our reviewers wrote: "Dr. Braaten claims that you will burn an additional 250-500 calories per day at cold temps. This seems low, indicating an amount of increase due to the basal metabolism (thermoregulation) functions alone, and may not consider the additional extreme physical exertion normally encountered under winter conditions." We gave Dr. Braaten the opportunity to respond, and she replied: "Most folks will dress adequately for cold conditions, so increased BMR is unlikely/insignificant. I agree, cutting new trail through three foot snow drifts would increase caloric needs substantially… However, I suspect that most of us will be following a blazed trail, or only occasionally putting out that kind of effort. Add to that shorter days (less daylight), and calories may come out about the same as they would under "friendlier" conditions."
BB: We're obsessive about mimimal fuel on longer treks in moderate weather, (see our website) but quite liberal when camped in subzero temperatures. Aside from more fuel required to heat water for cooking, we drink more hot fluids, and melt snow. Better to err on the side of safety.
RNC: the recommendation to take at least three times as much fuel for winter trips is known to be excessive. Experience suggests that a 50% increase is enough in Australian conditions. In addition, we can usually find water in our snow fields. However, if you have to melt snow that doubles the fuel requirements.
RNC: it would be rare for Australians to encounter this degree of cold, but we can face conditions almost as bad. It is easy enough to get wet in our snowfields, and once the sun falls it can drop quite easily to -10C. The combination of wet gear and sub-zero can be, and has been, lethal. On the other hand, you should be wearing enough clothing that you are reasonably insulated from the cold.
RNC: While everyone should know their own limits, I have strong reservations about the safety of continuing until one member of such a small party is this exhausted. And if one person is so exhausted that they have an accident, most other members of the party will be almost as tired. Maybe they should have been on skis!
RNC: The concern about food choices and prior food preparation is wildly excessive for Australian conditions. I agree about the need for food which can be eaten as you go for use during the day when the weather is poor, but we have enjoyed many fine lunches sitting in the snow in fine weather, way sub-zero. We have no problem cooking and eating a perfectly normal bushwalking evening meal - albeit perhaps a generous one. The use of an external kitchen is neither needed nor recommended in Australian conditions: you need to get out of the wind. The idea comes from some parts of America where they are very used to having dead still and fine weather in thick conifer forests. Cooking in the vestibule of the tent in Australia is standard. More drinks are needed as recommended.

Bibliography

Askew, Eldon W. Nutrition for a cold environment. Phys and Sportsmed. 1989, 17(12).

Rintamaki, H., T. Makinen, J. Oksa and J Latvala. Water balance and physical performance in cold. Arctic Med Res 1995, 54 Suppl 2:32-6.

Stroud,MA, AA Jackson and JC Waterlow. Protein turnover rates of two human subjects during an unassisted crossing of Antarctica. Br J Nutr. 1996, 76(2):165-74.