Daily calorie requirements for long term thru hikes?

[Kevin Burton]

When I go backpacking I usually compute how many calories I need to eat per day based on mileage and my weight and then pack that much food.

I did 2 weeks this year in Yellowstone and I didn't really eat THAT much. I almost had to FORCE myself to eat more than 3000 calories per day.

I was burning about 6000-9000 calories per day though as I was hiking 10 or more hours.

This leaves a significant calorie deficit. At lower V02/heartrate that means I'm mostly just burning through fat stores (which I won't object to).

On about the 13th day, I kind of ran out of energy. I'm not sure why but at about 2pm I just felt like crap and went to bed and didn't wake up until the next morning.

This could have just been a fluke of course. It was the second to the last day so I'm not sure what would have happened after that.

It isn't REALLY sustainable though without losing a lot of weight.

Does anyone have any thoughts here?

All the PCT thru hikers I see are rail thin :-P

For smaller treks it will probably work as a way to lower pack weight. Just not sure about a 4 week thru hike which I'm planning this summer.

[Franco Darioli]

"I was burning about 6000-9000 calories per day though as I was hiking 10 or more hours."

That seams a bit high to me…
A top Tour De France rider burns about 6000 calories per day.
Granted they only race 4-6 hours however at speeds over 25MPH on average.
running at 4mph burns about 7 calories per minute so well under your figure too.

http://kodjoworkout.com/2012/08/how-many-calories-do-olympic-athletes-burn/

[Ian]

Just wondering if your diet was heavily weighted towards fat/protein. Any possibility you burned through your glycogen stores and hit ketosis? I know when I hit that point I'm a little groggy for a couple days.

Powerbars work well for me when I hit a wall.

[Hiking Malto]

Let's be clear on terminology. When you say long term thru, are you meaning a couple of weeks or months?  I take it as months yet you gave a two week example.  That distinction makes a HUGE difference.
 
You didn't give any details on daily mileage, your weight (including pack, elevation gain etc. so it's tough to be specific.  But my rule of thumb on high mile days with significant elevation gain is you will burn 1 calorie per pound per mile.  In my case, fully loaded out, I weigh 200 lbs so 200 calories/mile is my estimate.  So for a 30 mile day, I would expect to burn 6000 calories and a 40 mile day would be 8000 calories. So I'm a bit skeptical on your 9000 calorie number unless you were doing 40+mile days with 10k elevation gain or 30+ miles with a total weight of 300lb.
 
So let's make some assumptions.  Let's assume you are talking two week trips AND that you have a few pounds of fat to spare.  If you say you don't, I will call BS :O Why?  I was in search of the HIGHEST CALORIE DENSITY to minimize the weight of say a 3500 calorie load.  I now realize how absolutely wrong that approach is FOR THE SCENARIO I LAID OUT ABOVE.  Why?  It was way too high in fat and the protein was wrong.  I had macadamia nuts, cashews, peanut butter, olive oil, all of the good high-density foods that always get talked about to minimize weight.  But I was doing nothing more than carrying spare fat, my body already had more than enough fat stores to do a trip like the JMT or your trip listed above.
 
Two years ago after a snowshoe trip, posters here (Greg and Tom) suggested I look at a higher carb food carry.  That thread changed my hiking forever.  While I went the route of drinking my calories in via Maltodextrin, how the carbs are consumed is less important than the total carb load.  I have been thinking about how to explain this for months now because I believe many are following in my earlier sub-optimized footsteps.  Let's look at some numbers.  Two scenarios, both using ideal foods with zero water etc.  Both have a weight of just over 40oz.
 
Scenario 1 – Optimized weight load (high fat) – 7000 calories
Fat – 41%
Carb- 41%
Protein – 19%
Food weight – 40oz., theoretical calorie density 172 cal/oz.
 
 
Scenario 2 – High carb load. – 5200 calories
Fat – 10%
Carb – 70%
Protein – 20%
Food weight – 40oz., theoretical calorie density 128 cal/oz.
 
Which diet will fuel you better?  What I have found is diet number 2.  Why?  Diet number 2 has 3200 calories of carbs which at 100 calories per mile will easily fuel 32 miles/day and beyond day after day.  At 32 miles per day I would have a calorie deficit of about 1200 calories which could be sustained for a couple of weeks. On the other hand the high fat diet has less than 1900 calories from carbs.  While this could likely work for a day or two, I suspect many would eventually deplete their gyclogen stores and end up fading in later days.
 
So in summary, get rid of the fat.  Leave the peanut butter, nuts and olive oil at home, or save them for a multi-month thru hike where they are absolutely required. 
 
Please note that the numbers that I used are my best estimates for me and will vary from person to person.  Look beyond the number to the concepts behind them.  This concept does not apply to multi month thru-hikers, they can not rely on fat storage and need to look at overall calorie consumption in addition daily fueling. And finally if you are doing low miles, under say 20/day then you can likely eat anything you want, it won’t matter.

[Art …]

Greg I like reading your fueling comments, you clearly have done a lot of personal research.

point one – I think you have a typo, shouldn't scenario 2 read 130 cal/oz ?

point two and question –
assuming 40+ mile days, there must be a difference between 40 miles in 10 hrs and 40 miles in 17 hrs and the optimum carb-fat ratio of your food source. I've read that at slower paced sustained activities the body can utilize a fat based food source better than at higher speeds.
where would you think the cross over point is ?

[Hiking Malto]

Art,
Thanks, corrected the cal/oz.

As far as the second point. I starting building a mathematical model for the exertion vs. fat etc. (I have really gone deep on this). Here is the simple way I'm looking at this right now. Above a certain point (the whole range we are talking) your body will process as many carbs as possible. I'm am using 300 cal per hour which is on the high end. hammer says 250-300. This value would be fixed. The variable is how fast your body can process fat which will impact how quickly your glycogen levels drops. The higher the exertion, the higher the calorie burn AND the lower the fat burn would be because that will impacted by reduced oxygen. (I still need to research this to make sure I have that right.). So exertion would not impact the target carb consumption, it would impact how long you could sustain this. There will also be huge variation due to fitness level on fat/exertion impact.

As an aside I think the whole concept that you see in gyms around fat burning zones etc is very misleading. All of it burns glycogen and the body will replace it with carbs where available and fat

Any thoughts?

[Art …]

my interest in all this is strictly in the under 2 week area,
you guys who love to spend months on the trail are a different story.

my interest is also purely a weight saving issue, see if I can reduce pack weight by 1-2 lbs. with a higher fat content diet.
if not for that I would simply drink Perpetuem the whole time.

I seem to have read somewhere that its possible to train the body to burn fat intakes better while at high intensity. not sure the specifics, have to try and find it.

I've tried too many nuts in the past, won't go there again.
But I'm starting to test these manufactured wafers called Stingers.
very very expensive, but they go down easy without much water.
content is :
7g fat
21g carbs
0g protein (figure I can get this at night)
that = about 151 cal/oz and about as far up the scale as I'm willing to go.

jury is still out on these as a multi day food source, need more testing.

p.s. just thought of this since you are in to make your own.
what would be a good fat source to add to Perpetuem to get to the same Fat-Carb raio?

[Randy Martin]

Completely agree with what Greg says. I also wouldn't want to eat a certain way at home and then suddenly take a < 2 week backpack trip and eat a completely different way.

[Kevin Burton]

I've done lots of research on this topic and your numbers seem incorrect.

It's around 400-500 calories per hour to hike. Let's say 400. If you hike for 10 hours that's 4000 calories.

Then you have your burn rate just for living (BMR) and that's about 2000 calories for me. Normal camp activities actually burn calories so say another 500 just for screwing around and you're at 6500 calories.

[Kevin Burton]

No… not when backpacking. I'm usually on paleo in my day to day life and when I go backpacking it's WAY higher in carbs.

Mostly granola bars, oatmeal, dried fruit, etc.

[Kevin Burton]

"But I was doing nothing more than carrying spare fat, my body already had more than enough fat stores to do a trip like the JMT or your trip listed above."

Careful here. There is an upper bound on how many calories you can metabolize from fat per day without catabolizing muscle protein.

I think it's 31 calories per lb of fat…. I may be wrong though and will have to look it up but that seems about right.

After this limit you end up using both carbs AND muscle which is why you see endurance runners looking super thin. (though there is a selection bias here).

Also, I did fail to note that I WAS carrying a high carb load. I didn't actually break it out in terms of percentages but I could pull up my old spreadsheet and figure it out.

I was using your strategy too. Try to focus on high carbs but also get in some fat.

[David Thomas]

One problem with assigning a number of calories per mile or hour of hiking is whether you figure a TOTAL energy usage during that time or just the amount over basal metabolism (of 100-ish calories per hour if you are sitting down, reading a book).

I (at 180 pounds) take as a given a basal metabolism of 2500 calories / day (in maintenance mode. I'd aim for 1500 to 2000 calories per day if pursuing weight loss).

On top of that, of course, we vary in our body weight, hiking speed, and climb rates.

For me, I figure about 100 calories (above basal requirements) per mile plus 100-200 calories per 1000 feet gained or lost. That's a range because I gain elevation much more efficiently on a 5% slope, and somewhat less so at 10%. Above 10% and it is less like walking (something we bipeds do very well) and more like stair climbing – something we are not as efficient at.

Grand Canyon, R2R2R in a day: 2500 basal + 42 miles x 100 calories/mile + 21000 vertical feet x 150 calories / 1000 feet =

2500 basal + 4200 horizontal + 3150 vertical = 10,000 calories that a day.

Now, I didn't complete Eugene's most excellent R2R2R last year, I only went 28 miles that day. But on a shallower, 40-mile hike up here (only 4,000 feet total up+down), 7,000 calories serves me well. I'm not hungry, I don't bonk, I don't think I lose any weight that day.

-David

[Hiking Malto]

Kevin,
Please be spefic regarding weight, mileage etc. you also can't look at calories per hour unless you have a specific speed. I hike 3 mph pretty consistently so my 200 calories per mile comes out to 600 calories per hour. But I also very likely have higher elevation gain per mile and my 200 calories per miles includes basal calorie burn. That is why I specify that it is intended for high mile days. The 2000 base calories get spread out over a lot of miles.

Art, hammer put Lecithin in Perpetuem which is a fat. Not sure if it for the fat content, a processing aid or whether it has additional benefits. I originally added that to my Malto mix then removed because it tasted yucky. I would be more inclined to take something with coconut like my personal favorite Mounds. It is almost a 47-49-4 c-f-p. I would also reserve a good chunk of protein for the end of dy recovery meal. I am doing research to find what foods would make the best combo of glycogen recovery/protein and then fat if needed for cold or other reasons.

[Hiking Malto]

David in your example you have 21k in vertical feet. I don't think you are suppose to use the downhills. Cut your 3150 in half and you get a 1575 for a total of 8425. That is almost exactly the same as my estimate of 200 cal/mile which gives you 8400. I know that it isn't 10000 because I would have died burning that ratio of calories on the PCT. I had a very good idea of my calorie intake and weight loss since I primarily did mail drops and was engineeringly anal about the calorie load.

[David Thomas]

Greg,

My total number is probably high. Most everyone counts the up only, but here's why I count the down:

It is very clear to me that I use my muscles to lower my body down a step, even though I haven't done "work" in a Physics-class sense, I burned energy using my muscles. Also, I tend to get sore and less efficient for the rest of the day/week due to the downhill portion more than the uphill portion.

But I'll grant that downhill uses less calories than uphill (but more than level).

If I say 10,500 feet up at 100 cal/mile (it is a VERY well-graded trail) = 1050 calories and 10,500 feet down x 50 cal/mile = 525, then the total for vertical is 1525 like the 1575 you suggest.

But if there's a lot of rock-hopping, root-dodging, or stair-steping involved, then I'd go higher than the 100 calories / 1000 feet up and the 500 calories / 100 feet down.

When not considering caloric intake, but "how tired/sore will I be at the end of the day?" or "can I do a hike of X equivalent miles in a day?", then I like equivalent miles = horizontal + 10 x vertical. i.e. double the thousands of feet and add to the miles. 42 miles horizontal and 21,000 vertical up+down is like 42 + 2×21 = 84 flat miles. I find that comparison a good rule of thumb.

It is even easier in metric (as most things are): equivalent KMs = horizontal KMs + another KM for every vertical 100m.

[David Thomas]

Greg:

I've forwarded your thoughts on fat/carbs to a musher friend. On his first Iditarod (1000-mile sled dog race), he brought lots of high-calorie, high-fat goodies (pizza, brownies, etc) that you normally wouldn't eat at home. He was in great shape to start – lots of training dog runs and playing soccer – you wouldn't have thought he had any fat to lose, but 2 weeks later, he'd lost 3 belt notches and ate non-stop for weeks after returning.

Part of it was that while the dogs sleep 12 hours a day, the musher is going for 20 hours a day setting up camp, booties on dogs, prep'ing dog food, checkpoint logistics, etc. And how ever much you train in town, you ain't up for 20 hours a day for 2 weeks in your normal life.

But I suspect the type of calories he brought may have been a issue as well.

[Kevin Burton]

This is a great thread and it's great that as many people are math/science geeks as I am and obsess about this stuff.

It's clear that many of us burn from 6000-10000 calories per day.

I think my main question is what happens when you eat LESS than that …

At 250 calories per bar, and 8000 calories, one has to eat 32 granola bars (entire packet) per day to get 8000 calories.

Over 10 hours that's 3.2 granola bars per hour or roughly one bar every 18 minutes.

I would flat out explode if I ate that much!

… and certainly I would have to take a bathroom break VERY frequently.

I usually sit down every 2 hours and have 1-2 granola bars and maybe some trail mix or some fruit.

I'm no where NEAR my daily calorie requirements…

[Art …]

I'm a big eater, and I don't know that I've ever consumed 10,000 calories in one day, even during my cookie and ice cream binges.

from my ultra running research, there seems to be a limit to how many calories the body can absorb per hour, has to do with body weight, but I seem to recall 300-400 max.

I've done 36 hr non stop events where I averaged about 300 calories per hr and never felt depleted calorie wise.
not sure how I would feel after 2 weeks at the same level.

[Bill Segraves]

A few quick comments:

In my experience, 70-80 kg male trained athletes can be expected to burn approximately 6000-7000 calories/day during 10-12 hr trail days, traveling with relatively light packs for the equivalent of 30-35 miles on moderate terrain or 20-25 miles on rugged terrain with lots of up and down. If consuming ~ 2500-3000 cal/day, a weight loss of ~ 1 lb/day can be expected.

Appetite suppression during first two weeks of hiking is common, and I and my friends find it hard to consume more than ~ 3000 cal/day during that period. After two weeks, appetite kicks back in. With the right food, it's not hard to pound down 6000 calories/day. (In college, some endurance athletes I knew were hitting 10,000 or more.) YMMV, but I do not find it problematic to derive ~ half those calories from fat.

It's very important when looking at expected calorie consumption/hr for moderate activity to know whether it includes basal metabolism. Whether activity at 400 calories/hr includes or does not include basal metabolism on order of 100 cal/hr has a major impact on the overall caloric needs calculation. These differences are amplified given that the caloric needs approach zones where marginal effects can start to become significant (e.g., any time you're near your capacity to process food).

By my reading of the literature, the switch from burning fat to burning carbs is not as dramatic as many people seem to perceive it to be. It's only at very high intensity that fat burning stops being able to make a significant contribution. No one's out there backpacking at 90% of VO2max, and if they are, they're not going to be doing it for long. (If you're the exception, someone should work you up and write a paper about you, after you get your medals.) If you read things differently, let's hear it, preferably with references.

Cheers,

Bill

[Hiking Malto]

Running a calorie deficit is not a bad thing….. In fact I believe it is a very good thing and something that should be planned. No doubt that Art ran a huge deficit but he eat enough carbs and his body provided the fat. I think this is also the same with the Iditorod guy.

I want to address Kevin's 8000 calories of granola bars. Looking at a random Nature valley bar it was 1/3 fat. So, switch out the granola bars for say maltodextrin and you would only need to carry 5500 calories to provide the same energy from carbs, your body again provides the fat. How much is 5500 calories of Malto? I just filled another batch of my magical Malto mix and each 16.9 oz. bottle holds 1200 calories. (either the Honeyville Malto is higher density or I weighed the previous batch wrong). So 5 water bottles full of Malto would give you 6000 calories. But there is no way I would try to eat calories equal to my expenditure unless I was doing what I call a long duration hike.

A long duration hike is one where your body is not able to provide the fat required to make up the calorie deficit. So in that case calories in has to equal calories out. This is exactly what most thru hikers go through at least on the second half of their trip. In my case I only lost two pounds in the last 1500 miles. How can that be done efficiently? Well one option is to pig out in towns, binge eating but that doesn't work real well if you don't do zeros. So how to eat 7000 calories which is close to what I was burning each day on the trail.

The same carb strategy was used, roughly 300 calories per hour. This provided the fuel that powered me each day and I never bonked during this time, in fact only bonked once when I was short of food in SoCal. In addition the end of the day becomes critical. I would eat a healthy dose of carbs to replenish glycogen, protein for recovery and a very healthy dose of fat for my body to process overnight. Finally I introduced fat into my diet during the day. My lunch had a lot of fat, peanut butter so it gave me a source of fat to process all day. The second goal, beyond not bonking was maintaining my weight enough to get me to the border. If I had to do it again I would likely pay a bit more attention to the fat content in the morning but I think it really just boils down to eat enough overall calories.

Even with eating enough calories you can still bonk. I hiked with a guy that was a much stronger hiker than I was. He had run a 3 hour marathon and was a stud. But he starved himself of carbs too much during the day and he would hit the wall. I was able to finally get him to eat more carbs during the day and it improved his consistancy.

[Ian]

There is a ton of good information in this thread and I’ve learned a lot.

I would like to offer a word of caution in that there could be other causes for the exhaustion such as a pathogen, blood anomaly, or other nutritional deficiency unrelated to caloric deficit; at least you now have a base line to work off of. You will have numerous opportunities in the future to reproduce those conditions and play with the variables. It wouldn’t hurt to have your blood values checked if this reoccurs and consulting a physician is never a bad idea.

Please update this thread when you think you’ve solved the puzzle.

[Diane “Piper” Soini]

On a truly long distance hike it takes a few weeks before the reality hits you. Then the hunger hits you hard. You basically can follow your hunger. You do not need to micro-manage your calories.

If your trip is long enough and you didn't estimate your food needs correctly, you can throw away unwanted food (or leave in hiker boxes) or purchase additional food. You spend a lot of time gravely eating as much as you can on your resupply days, too. In that way, there is no need to worry too much how precise you are because your body can withstand a period of insufficient food just fine but as soon as food is available, it will tell you what to do.

Your hunger will help you find food. You get really good at begging, mooching, looking really hungry with big puppy dog eyes at just the right moment, intuitively knowing how to find the restaurants in town with the biggest portions, how to find restaurants close enough to the trail for a short detour, etc.

I'm assuming your long distance hike would be on one of the national scenic trails and not in some totally remote or arctic place with no access to other people.

[Anonymous]

"my interest is also purely a weight saving issue, see if I can reduce pack weight by 1-2 lbs. with a higher fat content diet."

Since you are not doing thru hikes, why not make use of body fat and use a high carb diet to support its metabolism? It will enable you to reduce your carried food weight by however many body fat calories you can spare and the duration of your trips.

"I seem to have read somewhere that its possible to train the body to burn fat intakes better while at high intensity. not sure the specifics, have to try and find it."

It is a function of your VO2 max. The more oxygen you can deliver to your muscle cells the more efficiently you can burn fat at any given level of exertion. My hypothesis is that this also applies to efficiently utilizing fat at higher elevation; the greater percentage of what oxygen there is at higher elevations that you can extract and deliver to your muscle cells, the more efficiently you will metabolize any substrate at a given level of exertion.

This link gives a pretty straightforward explanation of the variables and processes involved, IMO.

http://www.uta.edu/faculty/blevinsj/August%2026/metab2%20notes.pdf

[Anonymous]

"Careful here. There is an upper bound on how many calories you can metabolize from fat per day without catabolizing muscle protein.

I think it's 31 calories per lb of fat…. I may be wrong though and will have to look it up but that seems about right."

Could you supply references for this, Kevin? This is the first I have ever heard of such a limit, and I would like to know more.

[Anonymous]

"I'm no where NEAR my daily calorie requirements…"

You have to be supplying the energy from somewhere to perform the work necessary to complete the requisite number of miles. The answer is almost certainly body fat, at least on trips less than, say, 2 weeks, depending on your body composition.

[Author]

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