Backpacking Science and Privilege: Food

On long-distance backpacking trips we don’t take the same things for granted that we do at home and as a result we can gain some insights into our privilege and how it affects the way we hike our hikes, and pack our packs. In this series of three posts I’m going to talk about how science and privilege influence the way I pack my pack. Using science as my guide, I’m going to break the discussion into three parts (requirements for physiological homeostasis in the wilderness):

1. Food: Our ability to regulate blood sugar levels (glycoregulation).
2. Water: Our ability to regulate water and minerals (osmoregulation).
3. Shelter/Heat: Our ability to regulate body temperature (thermoregulation).

Unpacking my Invisible Knapsack: Food

In 1989 Peggy McIntosh wrote a famous essay in which she likened privilege to “an invisible weightless knapsack of special provisions, maps, passports, codebooks, visas, clothes, tools and blank checks.” What follows is a list of food based privileges that hiking the trail has made me more aware of:

• I don’t have to be hungry. Middle-class privilege means that this is usually true for me. On the trail, as long as I plan appropriately this remains true.

• Being hungry won’t hurt me or interfere with my ability to function. I am hypoglycemic, so both on the trail and at home I need to be careful about what I eat.

• I’ve never had to try to sleep with hunger gnawing at my stomach. Middle-class privilege means that this is usually true for me. On the trail, I run calorie deficits so large that this is no longer true… sooo hungry.

• I know that if I need food other people will share their food with me. White privilege, middle-class privilege, and being a woman all probably contribute to the fact that this is a privilege I’m likely to get. On the AT this privilege becomes more obvious, and some people seem to rely on it.

• As long as the food I eat is fit for humans it won’t make me sick. Food allergies and intolerances mean that this is not a privilege that I can always rely on.

• I have enough body fat reserves to run a calorie deficit without compromising my short or long-term health. This is typically true for me. When I started the AT I was overweight and could definitely afford to run a calorie deficit and lose a lot of weight without compromising my health. As I head out to hike the PCT, I can’t rely on that nearly as much (see the science section below).

• There are stores accessible to me where I can exchange money for food. Middle-class privilege means that this is typically true for me. On the trail, there are not always stores accessible to buy food when I am hungry. Access is limited by the remoteness of my location.

• I know how much food and what kind of food I need to bring with me on a five-day backpacking trip. I have a lot of backpacking experience as well as access to resources that all allow me to have a good sense of what to pack for food and how to pack it.

• What I eat, how much, and/or how often is not something people make comments about. I think that this should be true, but it isn’t. I thought gaining thin privilege would make this true, but it didn’t. Do you get this privilege?

• My appearance and social standing are independent of my metabolism, what I eat, and how much I eat. On the trail this was true.

• The research that I use to determine how much food I should eat is based on people who look like me. White privilege means that this is largely true, however, most of the data is based on men and not on women.

• I don’t have to worry about where my next meal is coming from. Middle-class privilege means that this is usually true for me. On the trail, figuring where your resupplies are going to be and where your next meal comes from becomes more important.

• I can afford the healthiest, lightest weight food available. Middle-class privilege.

Though all of the above are likely to influence the amount of food I pack and the type of foods I pack, there are some guidelines based on science that you can follow to help determine the minimum amount of food you should carry.

Packing My Pack: Food

The amount of food that you need to carry depends on the number of calories you are likely to burn during your trip. The military probably has some of the best research about calorie consumption while hiking (marching) over long distances on rugged terrain with a pack. They suggest that people engaged in prolonged physical activity (like backpacking) need to consume 4000-5000 calories per day and that those numbers are even higher for cold conditions. The numbers calculated for recreational backpackers (using the heart rate method of energy expenditure by Hill et al ) are similar to those determined by the military, suggesting that backpackers typically expend 5000 calories per day. Despite burning 5000 calories a day, most backpackers were only consuming about 2000 calories a day, which is consistent with what I observed among 2013 AT thru-hikers.

Why don’t backpackers carry more food? Food is heavy. Most trail food is 100-200 calories/ounce, so to get 5000 calories/day you need to carry between 1.56 and 3.13 lbs of food per day. Assuming an intermediate calorie density and assuming that you want to maintain your existing body weight, you should be carrying about 2 lbs of food per day. So, assuming a five-day interval between resupply options, you should carry about 10 lbs of food. If there is significant probability that you will encounter detours, delays, or want ad hoc flexibility to extend the amount of time between resupplies, you may want to pack extra calories.

If you have sufficient body fat reserves to healthily maintain a calorie deficit you can carry less weight in food. Most AT thru-hikers carried between 2000 and 3000 calories of food per day, which works out to be about 1 lb of food per day. On my AT thru-hike I ran a significant calorie deficit. I lost 50 lbs.  Assuming that each pound of lost body fat is equivalent to 3500 calories burned, that means that I ran a net calorie deficit of 175,000 calories. Since I was on the trail for roughly 150 days, that works out to an average calorie deficit of 1167 calories/day.

For my PCT hike, I can’t afford to run a calorie deficit that large. Based on my current weight I figure I can lose a total of 10 lbs (a net 35,000 calorie deficit) on my hike of the PCT without becoming unhealthy. Assuming that the trip takes 150 days (the same amount of time I was on the AT), I can run an average daily calorie deficit of 233 calories.

As our calorie deficits on the trail climbed we put more and more effort into maximizing the calorie density of the foods we carried. Though the range of calorie densities for trail food was typically 100-200 calories/ounce, we all started to add more calorie dense items to our resupplies as we got further into our hikes. Which foods are the most calorie dense? Fats! (Here’s a list of the most calorie dense foods). Fats have 8.8 calories/g or 246 calories/ounce, and so high fat foods become very popular on the trail. To get more fat into my diet I carried things like Justin’s Maple Almond Butter (190 calories per 32 g or 166 calories per ounce) and packets of olive oil (240 calories/ounce).

In addition to carrying more calorie dense foods, we tried to help make up for our on trail calorie deficits with calorie surpluses in town. Ice cream, pizza, oreos, doughnuts… all of the most calorie rich foods we could find we ate. Though fats are the most calorie dense foods, the runner up (Ethanol, at 7 calories/g or 196 calories/ounce) was incredibly popular in town. Using ethanol as your major source of calories has some significant downsides however, including (but not limited to) hangovers and dehydration. If you get dehydrated in town, you need to carry (or otherwise procure) more water on the trail and water is heavy (1 L is 1 kilogram, or 2.2 lbs)!

In the next post I’ll discuss how privilege and science influence the way that I deal with water on the trail.

 

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Are there other ways that privilege and science influence your relationship with food and how much food you carry?