Body Fuel: How to Eat for Performance

Body Fuel: How to Eat for Performance

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Disclaimer-Please Read

***I am no expert and no doctor. The information I'm providing here is an opinion, one of many at that. I welcome people to correct me or disagree. One thing I don't want is so many details that the basic and important message here is lost.

The point of this article is not to preach my opinion or for me to be right. Please add your feedback so WE can provide information to take us farther!

Thanks go to Steve Larsen for his help with this article.

See also: Learning to Rock Climb


Climbers often spend as much time planning trips as they do on them. Pre-trip packing is more than a chore, it's a ritual. Weight is cut anywhere possible. Racks shaved down to bare essentials. Everything is geared towards success without excess. Yet many of us pay more attention to the fuel that powers our stove than the fuel that powers our lives.

Food and Hydration are key to the success of any physical edeavor. Physical performance is largely a function of the inputs available to the body to create energy. The type, amount, and timing of what you eat will affect your body's ability to function. Optimizing our intake helps optimize our performance and increase our chances of safety and success.

Strenuous activity = Aerobic activity through Anearobic threshold. Hiking or climbing, sweating a little with a hightened respiratory rate

What is food?

Food is made up of Carbohydrates, Proteins, Fats, Vitamins, Minerals, Fiber, and Water. Though Vitamins, minerals, and fiber are important, to maximize perfomance we will look at Fat, Carbs, and Protein. Vitamins and supplements are best left for their own article.

Carbohydrates: Carbs are the fuel of life. Carbs are the main fuel our bodies run on, the "gasoline". Carbs come from many places and make up the brunt of most of the food we eat. Carbs convert easily to Glycogen which is the most common energy source of the body.

Protein: Protein is the building block of life. The body uses protein to rebuild muscles and fuel cell growth and regeneration. Protein is made up of amino acids. There are essential amino acids and non-essential. Non-essential acids can be produced by the body while essential amino acids must be ingested from an external source. "Complete" proteins contain all the essential amino acids, flesh (meat) is a complete protien, complete proteins are harder to come by from vegetarian sources.

Fat: Fat is a climbers best friend when utilized correctly, the "octane". Fat is, among other things, an energy storage medium for the body. Fat contains twice the potential energy of protien or carbohydrates. Unfortunately fat has adverse health effects too, therefore finding a healthy source is important (more on this later).

Calories: A calorie is a measure of energy, of heat particularly. A calorie is the amount of energy needed to heat 1 gram of water 1 degree centrigrade. Calories you see on food labels are actually Kcal (1,000 calories) but are referred to simply as "calorie".

What is Energy?

Your body runs on Glucose. The body makes ATP from glucose that powers most body functions. The energy used climbing will come from Glucose.

Where the body gets Glucose is a more complex tale that depends on two things:

-What your body has on hand
-How hard you're working

Sources of Glucose:

-Glucose in the blood stream, "blood sugar"
-Glucose derived from Glycogen (a long chain of glucose molecules)
-Glucose derived from metabolized Fat
-Glucose derived from metabolized Protein

Glycogen, Fat, and Protein are energy storage mediums.


When the body gets Carbs it will do one of two things:
-Make Glycogen
-Make Fat
it depends on what your body needs

Glycogen is what climbers run on most of the time. The body makes Glycogen, a long chain of glucose molecules, from Carbs. Therefore, an alpinist's diet should consist mainly of carbohydrates while climbing. Carbs can be converted to energy more quickly than fat or protein. Carbs translate into energy better than any other source during strenuous activity Carbs are easy to find, they make up most food.

Glycogen is THE fuel source during highly strenuous activity. Unfortunately glycogen has a downside, the body exhausts its supply quicker than fat. Once glycogen stores are depleted the body needs time and food for recovery (up to 24hrs), even if there's plenty of fat on hand. This explains why we get tired quickly when we're really working hard.

Once glycogen stores are depleted the body starts metabolizing glucose from other sources like protein, the body's best source of protein is muscle tissue, it's in our best interest to keep our bodies form eating our muscles, more on this later.

***A climber should try to eat at least As many grams as possible of carbs per day while climbing.


Protien is an essential part of muscle regeneration. Muscle regeneration is difficult during highly physical activities so protein is best eaten during long periods of rest and at night before bed.

Protien can be difficult to come by. Flesh is the most obvious source of protein (muscles actually are mainly protein). Nuts, lentils, certain grains (namely quinoi), beans, and some vegetables are good veagan sources.

The body can use protein as an energy source if your body lacks carbohydrates (glycogen) or cannot access fat for energy. It's important that your muscles get adequate protein for regeneration and growth, try to plan your protein and carb intake so that the body uses carbs for energy and protein is used for recovery. A good way to keep protein as protein is to eat it before prolonged rest as opposed to before and during activity.

Don't eat enough protien and you'll pay for it.

***A climber should try to eat at least 40 grams of protien per day while climbing.


This entire article boils down to how to utilize fat. Fat contains 9 calories per gram, while carbs and protein contain 4. This means that if we can burn fat we have a nearly inexhaustable fuel source.

If we can burn fat we can go all day. Your body burns fat best at about 50% maximum exertion. Beyond that the body starts to need energy quicker than it can be metabolized from fat. As a general rule once you can no longer reasonably breath through your nose or talk you are probably no longer burning fat.

What's important: Stay around 50% of your max heart-rate and you will maximize your endurance. Continuous cardio-vascular training teaches your body to burn fat and release more fat when your optimal fat burning zone is reached.

***A climber should try to eat at least 35 grams of fat per day while climbing.

Aerobic Activity

Aerobic activity occurs a bit above a resting heart-rate and below your anaerobic threshold. This is your optimal fat burning zone.

Continuous cardio-vascular training will teach your body to burn fat and release more fat when this zone is reached. This means that if you train your body to burn fat and you stock up before you leave on a trip you can kick ass all day.

As a general rule your optimal fat burning zone occurs at about 50% of your maximum exertion.

You should be able to breath out of your nose and talk reasonably during aerobic activity.

Anaerobic Threshold

Your anaerobic threshold (AT) is near your max heart rate, it represents the upper level of your physical ability. Being beyond your AT will exhaust you within minutes, recovery can take a long time. Beyond your AT your body cannot supply enough oxygen to support metabolism of energy sources, so once you go through you blood sugar, you're toast.

A very simply method for estimating the anaerobic threshold is to assume anaerobic threshold occurs at 85-90% maximum heart rate. 220- your age provides a quick and sloppy estimate. Heart rate varies greatly between individuals and even within the same individual so this is not the most reliable method. Better measures involve blood tests and/or carefull monitoring during activity.

As climber we want to stay below our AT. Going slower, calming down, or using energy saving technique will lower the heart-rate and allow your body to access fat as an energy source. This is not always possible, and given the excitement and fear we sometimes feel it's even harder. Still this and staying fed is our goal.

Once you AT is determined a heart rate monitor can help you practice staying in your zone. A HR monitor is a good idea for many reasons, it will show you your recovery times, warmup time, etc. It's a very useful tool.

Working Hard and Caloric Deficit

Caloric deficit:

When your body burns more calories in a day than it takes in, one is said to be in "caloric deficit". This is a common reality for climbers. If the body doesn't have enough energy from fat or carbs it will metabolize it from Protein. It's possible to burn 10,000 calories in a day, try eating that much!

Working Hard:

When the body really starts to work hard it's energy sources become limited. Remember that the body get's Glucose (energy) from blood sugar, glycogen, fat, and protein. As you go up in heart-rate it get's harder to metabolize fat and blood sugar burns off quickly. Glycogen will pick up the slack, making up a larger and larger portion of energy use. If glycogen runs out the body will use protein to make up the difference.

Problems burning Protein:

The body can get protein from two sources: ingested protein and muscle tissue. Even if your body eats the ingested proteins that means it didn't go to your muscles, so either way muscles suffer. If protein is used as energy for a prolonged period of time recovery is slow, the multi-day outing is stuffed, and protein intake is very important.

To combat the negative effects of metabolizing protein and caloric deficit we need to be:

-Well fed
-Burning Fat (pay attention to activity level)

If you're going to be working really hard all day you need to really build up your Glycogen reserves before you leave and eat lot's of carbs during activity. Burning fat minimizes glycogen use and helps keep you body from burning protein.

When and what to eat

Before the climb: Load up!

Before you go on your trip you should try to load up on everything. Drink tons of water (see the hydration section), eat lot's of fat (try to make it healthy fat), eat lot's of protein, and "carbo-load". It's often not possible to eat enough to keep up with calorie expenditure on intense climbs so loading up early can help.

During activity: Carbs!

As a general rule try to eat carbs before and during activity

Protein and fat are both more difficult to process than carbohydrates. They take more time and energy to become useful. Protein and fat serve important functions best while at rest. Give your body time to use the materials wisely. That said, it's totally fine to eat whatever during activity, but carbs will work best.

During strenuous activity your body can only process so much food without detracting from performance. In general, assume your body cannot take in more than ~200 calories per hour during high activity. This probably won't keep up with your calorie usage but it's the best we can do.

Carbohydrate Gels are engineered specifically to be eaten during high activity levels. They are packaged in a dosage that the body can handle without detracting from performance. Made mostly of simple carbohydrates, carb gels pretty much equal "instant energy". Many people loathe the taste and are leary of the idea, but there is no better instant fuel source. They also take very little water to digest. Candy also works well.

During long periods of rest: Protein, Carbs, then Fat!

Your body can run on protien if it has to, but muscles suffer. Give your body protien before bed so that it can use it to repair muscles overnight. Your body also needs to rebuild Glycogen reserves so Carbs are important. A 4:1 ratio of carb/protein during the first 1.5 hours after stopping for the day serves both functions best. Wait another hour or two before you eat a lot of fat, this lets protein do it's thing.

Fat is a great energy source but even it needs replenishment, before bed is the best time for you body to be able to digest and store fat, and it'll help keep you warm! Eating fat and protein just before long periods of rest or at the start of them gives your body more time to digest them.

After the climb: Protein!

Lot's of protein to regenerate muscles, lot's of fat to rebuild reserves, and lot's of carbs. Since carbs come from everywhere don't worry about them and just try to eat lot's of protein, carbs come by proxy.


Being well hydrated maintains high blood volume, which in turn provides muscles with more oxygen, which means you perform better. Staying hydrated, and hydrating well before you leave will make a huge difference. Salt helps the body retain water, it is depleted when you sweat, eat lot's.

Before the climb: water

Drink a lot of water before your trip. Try to drink a gallon for three days before you leave, and two gallons the day before you go. Eat salt.

During the climb: WATER!

In the cold, heat, at altitude, and during strenuous activity you lose more water than normal, so to stay hydrated you must drink more.

2 Liters minimum per day. More is better.

As a general rule try to drink a mouthfull of water every ten minutes. If you run out, take the time to get more, you'll probably make the time up in performance and your recovery will improve drastically. If you're thirsty, you're already dehydrated.

Hydration Bladders:

A hydration bladder makes adequate intake easier, and therefore more likely to actually occur. You will simply not stop to take out your nalgene often enough, you'll drink too much in one sitting and not enough overall. If hydration is truly important to you a hydration bladder is essential. If it's too cold a bladder may not be an option...

Am I Dehydrated?

An accurate and easy way to judge you hydration is to watch the color of your pee. It should be clear or light yellow. Yellow or orange pee means one of two things: you're taking a lot of vitamins, or you're not properly hydrated.

Good sources of Fat

Fat can be very bad for you. It can clog your arteries and defeat the purpose of loading up on it.

Try to eat MONO-UNSATURATED FAT, this is currently believed to be the best for you. There's saturated and unsaturated fats, with unsatured further divided by poly and mono. Saturated fats are generally solid at room temperature.

There are now butter substitutes that don't contain hydrogenated oils. Hydrogenated anything is bad for you. Real butter is pretty much pure saturated fat, not good. Try finding a non-hydrogenated butter substitute, they also make cooking oil.

Good pre-game sources:

-Avocadoes (I try to eat 6 the night before I go)
-Cooking oils: olive oil, vegetable oil, smartbalance, etc.
-Non-hydrogenated butter substitutes
-Fish (hopefully non battered)

Good sources while out (difficult):

-Cream cheese
-Nuts including peanut butter
-Cooking oils (bring a small container full and add to freeze dried food)
-Butter and butter substitutes
-Powdered milk
-Little half & half packets for coffee

it's tough find a healthy source of fat the works in the field. Do you know one? Please contribute your suggestions...


  • Pay attention to food labels: See what's in your food plan accordingly
  • Eat a lot: Bring enough calories, be disciplined and keep eating even if you don't want to
  • Eat often: Pop a carb gel every 20-30 minutes during activity and come home feeling fresh
  • Eat salt: Salt helps you retain water and create electrolytes, eat lot's. Eat a bunch before your trip to raise blood volume
  • Plan for your trip: Take the time and add up the calories. You need at minimum 2,000 calories a day to keep performing well, 3,000 is much better, above 4,000 is probably not realistic. Bring enough fat and protein!
  • Bring variety: It's often easier to eat more if you have a variety of items to choose from

If you take this seriously you'll be amazed at the results.

If you only remember this

  • Eat carbs during the day, eat fat and protien at night

  • Drink a mouthfull of water every ten minutes, hydrate well before the climb

  • Try to take in about 200 calories made of simple carbs each hour during activity, spread intake out

  • Try to stay at an activity level where you could breath through your nose and not have to much trouble talking

  • Don't run out of Glycogen, Don't forget to eat Protein, Don't come home weaker!


Paying attention to what goes into your body can make a big difference in your performance. I've tried to provide enough information for all this to make sense, but not so much as to be confusing. You can certainly go much further down the rabbit hole.

I hope this was helpfull. Is an ongoing project.

Constructive crititcism and counter-points are most welcome.


See also: Learning to Rock Climb


Post a Comment
Viewing: 21-31 of 31

Travis_ - Oct 27, 2006 1:54 am - Hasn't voted

Re: Gels

Or even better, if you look at the ingredients of the Cliff Gels, it is Brown Rice Syrup. Just buy brown rice syrup, add some salt, put it in one of those squeeze tubes and you have much more econmical energy gel.


packet - Oct 30, 2006 1:55 am - Voted 10/10

Re: Gels

Gels are wonderful for summit days. The flasks are by far the best thing you can get for them as those empties suck. Just have to remember to drink plenty of water when you take one otherwise you get a somewhat nasty stomach ache.


rockrat2 - Nov 1, 2006 1:22 pm - Voted 10/10

Re: Gels

Good idea, I hate the sticky packets.


jwclimbs - Oct 26, 2006 6:48 pm - Hasn't voted

Wonderfully Done!

Excellent read and great work with the format/outline so that us 'common folk' can follow. It is hard to speak technically and still balance 'too much info' vs. 'essential info'. You nailed it though. Great info on when to eat what! As my ice season kicks off, I can't wait to put in practice. Long hard climbs usaully follow a 2 hr slug through the snow. My routine last year was simply lots of water, a handfull of cliff shots and peanut butter granola bars...can't wait to expand.
Thanks! - JW


egabriel75 - Oct 27, 2006 2:33 am - Hasn't voted

Other Topic

Hi Scotty,
It's great that you set out to write this article and that you are welcoming feedback.
I personally suffer from gastro-intestinal distress and many times during races or early runs and climbs have to stop and run for the loo if i didn't have time to go before. I know it's not a very uncommon issue and it happens to many people, so it's a topic to be considered.
I mention this because i see you reccommend eating a lot of avocado before a trip to load up on good fats. I would like to add that avocados very high in fiber ( also very high in vitamin C ), which is actually very good, but eating that amount in a single day could cause some problems to some people. Fiber is a non-digestible carb and it helps clean your guts as it passes through your intestines like a brush, but high dosages like that could cause some distress.
Also i would like to recommend to people who have low tolerance to lactose ( a sugar found in milk and dairy ) to try Lact-Aid pills. Lact Aid is lactate, an enzyme that digests this type of sugar found in milk. Some mammals stop producing this enzyme a while after the lactating period ends. Others keep producing some amounts. This is a very helpfull way to enjoy a breakfast of milk and cereals and dim those bad gases that are produced by the undigested sugars.
I can continue on recomending not eating gas producing vegetables like broccoli, but this could go on and is really another interesting topic for those who's belly's sometimes bother...


Travis_ - Oct 30, 2006 1:41 am - Hasn't voted


this article and comments inspired me to write my own on energy gels.

Home Made Power Gels - Energy for Less



rockrat2 - Nov 1, 2006 1:23 pm - Voted 10/10

Nice article!

Good info and written so that even us slow hillbillies can understand it. Good job!

Diego Sahagún

Diego Sahagún - Nov 6, 2006 1:46 am - Voted 9/10

Good job but...

I'd extend in the hydration section, wich is one of the most important factors in the body fuel. I'd put the problems of drinking too much water, the best temperature of the water for being absorbed...


marauders - Nov 6, 2006 10:25 pm - Voted 10/10


Just wanted to give you a quick "thanks" for writing this article. Very simple and helpful with great information.

Michael Hoyt

Michael Hoyt - Apr 5, 2007 12:31 pm - Voted 10/10

A Well-written Article

If follows a logical progression and breaks the overall concepts into easily “digestible” portions.

My method for keeping performance high all day is to ingest a gorp-type trail mix (nuts, raisins, M&Ms, etc) and down copious amounts of my drink mix (powdered Gatorade mixed as directed with 1 package of Kool-Aid [flavor] and a cup of sugar [carbs] added to each half gallon of the Gatorade mixture). I’ve done this for years with excellent results, even on 15+ mile days over some pretty difficult terrain.

I might add, that at only 135 pounds, I drink about 1 gallon of the above mixture per day while in the mountains. I’ve never understood how most people, many much larger than I, manage with so little fluid. But then, at the end of the day, I’m usually in much better shape than they are.


Groundswell - Feb 6, 2008 1:11 am - Hasn't voted

Biker Food

First of all, great article. Because I am on the leaner side of the scale (145 lbs) I pay careful attention to fueling during climbs. I experimented with using my biking nutrition during long climbs and had great success. For gels i use hammergel in a five shot squeeze bottle. For fluids, water with some gatorade usually works. Then I mix perpetuem for my protein/carb mix with some endurolyte powder to ward off the dreaded cramps. Once the activity stops I drink some recoverite right before eating dinner. I climb/hike with guys who I could never keep up with. Now they try to bum stuff off of me. Check out They have great articles on fueling. See you out there.

Viewing: 21-31 of 31