Electrolyte needs and real food

"Richard Nisley has commented on it at some length and provided a table showing approximate ratios of fat and carb burn at different MET levels. I also read the relevant chapters from a college level exercise physiology textbook. What I learned is that the MET level of your exercise is the primary factor determining the ratio of carbs to fat as an energy source. You can improve that ratio to some degree by increasing your cardio vascular fitness, but the basic variable will always be the intensity of exercise."

I'm familiar with the chart, but it's only a small part of the story. As duration of exercise increases, so does utilization of fat, and there are additional metabolic adaptations that will come into play over time if glucose is limiting. (And what the body uses if given a choice is not necessarily the only way the body can do things. The range of physiological adaptation to varying conditions can be pretty impressive.)

If the right experiments have been done (to say how much carbohydrate or protein would be needed to support utilization of fat as the primary calorie source during long-term exercise), they're not reported or cited anywhere that I've seen.

Anecdotally, I am comfortable with backpacking diets that provide ~ 40% of 3000 cal/day intake from fat, even while relying on 1/2 pound/day of fat-burning (and presumably some small amount of protein catabolism) for the rest of my caloric needs. And there seem to be a number of backpackers who rely on chocolate (~50% fat calories) as their main snacking food.

Cheers,

Bill S.

"One thing on my mind is muscle sparing when deliberately operating at a caloric deficit. I have been reading some of the old BPL threads and came across one that addressed that. The general opinion appeared to be that operating at a significant caloric deficit would result in the body using both body fat and muscle to make up the difference. The opinion there was that is inevitable — no amount of exercise / muscle use would prevent it, nor would ingesting protein."

My understanding is that the body normally derives about 5% of its energy from protein. Every source I have come across uses that figure. So, I have chosen to take that as a given. Since protein accounts for about 10% of my carried food, there is about 18 grams left over after subtracting 200 calories as the 5% of a 4000 calorie/day energy expenditure. It is doubtful that this is enough to completely repair damaged tissue, so I assume there will be some catabolism of muscle tissue. I no longer take trips long enough to have a significant impact on my well being, but were I to stretch a trip out much beyond 2 weeks, I would give the subject much closer scrutiny, and probably add another 20-30 grams of protein to my diet.

I don't think the calorie deficit per se drives the process, however, in the presence of adequate carb supply. It is when you run out of carbs to support the metabolism of fat that the body will resort to breaking down more than the nominal 5% of protein. It is a more complex process that requires removing the nitrogen from the protein to produce a "carbon skeleton", as one exercise physiology text refers to it, before feeding it into the normal process of breaking the hydrogen bonds to produce ATP. The oxidation of protein also requires more O2 than either carbs or fat, again according to my exercise physiology textbook. This would seem to automatically make it a fallback position for the body, to be used only when more preferable sources of energy have been exhausted, as it is both less efficient and destructive to the body. Evolution is a harsh mistress. Below is a link to the book. I would not recommend buying it, on expense grounds alone, but if you want to dig a little deeper,
you could probably get it at your library.

It sounds as if you are saying that the body will use the protein you consume for energy (rather then taking it from muscle). I only wondered because that BPL thread seemed to doubt that. As I read the Hammer article, they would agree with you.

My presumption is that use of protein for energy needs to be thought of as ongoing throughout the day, not on a per-day resolution. Consider the Hammer information. If you are actually using about 300 calories per hour, then they assert that the body will want to get 15-45 calories from protein. If you are ingesting 120 calories per hour (the low end of their range, and considerably more than your figures) and have their 8:1 ration, that is about 13 grams of protein ingested. In other words, you are ingesting somewhat less than the low end of what is being consumed and considerably less than either the high end or the low end if 4500 calories is an underestimate.

It sounds to me as if their formula has absolutely no margin for error at best. Is there some reason not to make the drink with a bit more protein? Would added protein inhibit fat utilization?

Once again, I am assuming that the protein you ingest the rest of the time — while not actually hiking — is a Good Thing, but not related to the use of protein for energy during the hiking day.

–MV

"I'm familiar with the chart, but it's only a small part of the story."

To be sure, which is why I did some further reading before embarking on an experiment of one, with me as head guinea pig. I used it to benchmark my tests, and it turned out to be sufficiently accurate for my purposes.

"As duration of exercise increases, so does utilization of fat, and there are additional metabolic adaptations that will come into play over time if glucose is limiting. (And what the body uses if given a choice is not necessarily the only way the body can do things. The range of physiological adaptation to varying conditions can be pretty impressive.)"

That is also my understanding, with the caveat that it will be tempered by the intensity of the exercise. As you say, we have developed several fallback systems over tens of thousands of years to cope with feast and famine, fight or flight, and so on. They will come into play if the intensity of the exercise exhausts the carb supply before one runs out of fat, and ultimately if both fat and carbs are exhausted. I was on the edge of that condition once, on a 16 day un resupplied trip, and I'm here to tell you I would never want to repeat that particular mistake.

"If the right experiments have been done (to say how much carbohydrate or protein would be needed to support utilization of fat as the primary calorie source during long-term exercise), they're not reported or cited anywhere that I've seen."

I'll bet there are studies out there. I haven't delved into the subject beyond what I felt was necessary to come up with the minimal amount of food necessary to support my decidedly less than endurance backpacking trips. Greg has taken it considerably further, but neither of our efforts were rigidly controlled experiments that would support a scientific conclusion. n=1 plus n=1 does not a study make. ;0)

"Anecdotally, I am comfortable with backpacking diets that provide ~ 40% of 3000 cal/day intake from fat, even while relying on 1/2 pound/day of fat-burning (and presumably some small amount of protein catabolism) for the rest of my caloric needs. And there seem to be a number of backpackers who rely on chocolate (~50% fat calories) as their main snacking food."

You and I seem to be more or less in the same ball park. I am at about 35% fat for my carried food, and 55% carbs weighing 300 grams and 10% of protein. I'm not sure where body fat fits into your calculations. Do you take it into consideration to some degree?

Hammer Nutrition –

Don't forget that Hammer sells products, with a target demographic operating near or at the lactic threshhold for days on end. Some of us operate in that regime, but most do not. Individual variations in metabolism, fitness, and hiking styles far outweigh the rigor of their suggestions.

I am a big fan of a couple of their products (since about 1998) and for what I do, they work for me. But it was trail and error to get there.

Although Hammer is prolific in its "papers", I don't think that alone makes them
The Authority on endurance nutrition. Moderation is advised.

IMHO.

"Don't forget that Hammer sells products, with a target demographic operating near or at the lactic threshhold for days on end."

This particular paper mentioned their experience was with people operating at 75%-85%, or for extended durations — more intense than most of us. I know that makes their figures different from optimal for most of us, but I do not know just how to make that adjustment.

Any idea how the percent protein utilized for energy varies, such as with exercise intensity? I'm still trying to understand the apparent discrepancy between the protein they provide in their drink and what they say the body uses.

–MV

You just need to do some studying on how mammals utilize carbs, fats and proteins and in what order under exercise stress at different distances and time constraints.
I used to race endurance horses and trained both people and horses to do hundred milers in under 24 hours (Tevis and Western States) and week long events of just under 300 miles. Many of the riders ran half of the races to spare the horses. How both species utilize carbs, proteins and fats in what order and what they consume before, during and after a race and how they do it is very interesting. And yes, too much protein will inhibit how fats are metabolized. In some cases we wanted the horses to use fat reserves because we discovered they could, as opposed to carbs which cause metabolic problems, unlike the people, who can consume carbs with better results. So we actually did decades of experimentation both long distance and track racing, And we proved that they could use extra fat before breaking down muscle tissue and we began to use fat in the diet (vegetable fat) to train their bodies to do it. But we had to train them so hard that the liver would release signals that the carbs and proteins were indeed used up and to switch to fat. Extra protein causes all kinds of metabolic problems and in fact over stressed the kidneys, so a lower protein level on race day and before was how we went. This is the same for some people also but with carbs. What we learned with both people and horses is that things are ingested in a certain order according to the duration and reserves in the liver and muscles, and how one has trained the body to injest fuel during periods of high exertion. This is the key. When the stored and consumable resources reach zero, this signals the body to start utilizing muscle tissue and you don't want that. That is why people on long trails, like the PCT lose so much muscle weight in the Sierras, they just did not carry enough of the right food to make up for what they are burning and they have not trained their bodies to utilize what is best for them in high stress situations. Some of you here who have a background of fast packing know how you utilize foods and electrolytes and only carry those foods which per ounce will sustain you over longer periods of time than just a day or two. I do not think there are any pat formulas for people, you've just got to go out and hike/run/bike or whatever and see what works for your body type and how you utilize fuels.

"'Anecdotally, I am comfortable with backpacking diets that provide ~ 40% of 3000 cal/day intake from fat, even while relying on 1/2 pound/day of fat-burning (and presumably some small amount of protein catabolism) for the rest of my caloric needs. And there seem to be a number of backpackers who rely on chocolate (~50% fat calories) as their main snacking food.'"

"You and I seem to be more or less in the same ball park. I am at about 35% fat for my carried food, and 55% carbs weighing 300 grams and 10% of protein. I'm not sure where body fat fits into your calculations. Do you take it into consideration to some degree?"

Typically, I can go for about two weeks with 3000 cal/day intake. During that time, I'm losing about 1/2 pound/day when I'm doing 20-25 mile days. Most of that's fat (by various criteria), but a small amount is almost certainly coming from catabolism of protein. After two weeks, I up the calories, but I don't yet have good quantitation of my caloric needs after that, due to combination of monster meals during re-supply, consumption of fish, unmeasured extra consumption of my friends' food, etc. Probably on order of 5000 calories/day.

Cheers,

Bill S.

Many interesting ideas flying around. :) A few thoughts that came to mind overnight.

If you want to optimize for no protein catabolism, you need moderately high protein and high calories, with not too much from fat.
If you want to optimize the weight of your pack, you need to go for high fat.
As far as I can tell, there's no way to optimize along both dimensions simultaneously.

IMO, it's probably not possible to protect against protein catabolism completely if you're in caloric deficit, no matter what the macronutrient makeup is. There is a basal level of protein utilization for fuel, and that rate increases any time you're in deficit, and probably at least a little bit any time you're burning a significant amount of fat (I haven't looked at the primary sources on this last point, thus the probably). If you can keep your glycogen stores up, you'll reduce this catabolism, but if you're going hard enough that you can't take in food at the same rate you're burning it, you'll catabolize some protein. If you haven't catabolized too much, you can replace it after exercise (in a time window that recent research suggests may be wider than most people were led to believe by earlier research).

Personally, I'm not too concerned that I may catabolize a small amount of protein during a short trip or during the initial phase of a longer trip. It'd be interesting to know if there are ways to minimize it (and the answer may differ depending on whether you fix the # of calories or the mass of food), but I doubt that there's a lot one can do about it, beyond eating a reasonable diet.

From the practical side, what really drives my interest in these questions is what happens on a much longer distance hike. Is there a way to minimize protein catabolism and maintain performance while deriving a high proportion of calories from fat? So far, I'm not seeing evidence that a specific special diet (as opposed to any reasonable range of diets with different protein-carb-fat amounts) can do better than our own bodies' capacity to adapt to dietary variation. It seems entirely plausible that there are a hundred "right" answers.

I enjoy looking at the details of how food works or doesn't work, but in the real world, I pack 3000-5000 calories per day of a mixture of real foods and then eat whatever looks good for any given meal or snack. (I have backpacked with maltodextrin and/or whey and still do use them on the bike for large group rides and for races, when I want to take in liquid nutrition, but no longer take them backpacking.)

It seems clear that a wide range of diets work even for 1000-2000 mile hikes. Greg did fine with maltodextrin, or with chocolate-covered donuts (for his snacking, at least). Heather Anderson thrashed the PCT on Clif bars, cookies, chips, crackers and dried fruit. Skurka's and Dial's diets are nothing special (and don't exactly *look* healthy). They all work.

Whether more attention to diet is needed when one is going really hard is an interesting question, as is what constitutes going really hard. Anderson averaged over 40 mpd, but wasn't actually going hard (by her own description). She walked really long days. For a fit person, walking 3 mph with a 20 lb pack (plus or minus, depending on how recently re-supplied) is very comfortably within aerobic zone. She ate while she walked, and IMO this is actually the key to how dietary needs change with exercise intensity. Any reasonable diet that your stomach can handle will work. If you're going so hard that you can't keep up well enough with your caloric needs to take care of the rest at your meals, then you may have to start getting fancy. Or slow down. People who look closely at training regimens know that you don't go hard every day. High volume and high intensity (relative to fitness) is not something that can be sustained over long periods of time.

Have at it! :) If I've made errors, let's dissect 'em.

Cheers,

Bill

This is probably obvious, but I am stating it anyway: it seems to me that this whole discussion is for normal people on trips of up to a couple of weeks — i.e. usable by most of us most of the time.

* The goal is to use body fat for part of your caloric needs. Two obvious motivations come to mind — lower pack weight and a desire to lose body fat anyway.

* At some point a person has little enough body fat that this is not a good idea. Exactly how much that is becomes a discussable matter. I believe that earlier in this conversation Tom suggested that might be about 10%. Whether or not he is exactly correct, I believe that is in the ballpark. It is also leaner than most of us are.

* This discussion does not apply to really long trips, such as though-hikes, because after the first few weeks those people are at too little body fat for this discussion to apply. They really do need to ingest as many calories as they are expending, unless they want to lose significant muscle mass.

–MV

Fat Utilization – For me it is not a Goal but just a readily available "tool". My only goal regarding food is to eat enough to maintain my pace, and do it with a smile. When I get slow, or cranky, I know I'm behind on my intake.

Thru-hikers are not necessarily constrained to matching expenditures. Resupply happens every 5 or so days, and in addition to their resupply box they are also (generally) eating Huge amounts of food. Once your muscles, and liver, and blood are saturated, the rest goes into storage as fat. Blogs are rife with stories about entire pizzas and pies disappearing, as well as the serial demise of a double cheeseburgers, fries and shakes. Only to be repeated again for dinner. So the cycle starts again.

"When I get slow, or cranky, I know I'm behind on my intake."

Yep, I think that's the best thing to pay attention to. I'll be going from 2000 to 2400 calories on my next trip.

I figure if I'm lethargic, hungry and cranky then I need more fuel.

Mostly carbs in the day for energy. Fats and protein at night, I think it helps digest slower and aids recovery during sleep.

"It sounds to me as if their formula has absolutely no margin for error at best. Is there some reason not to make the drink with a bit more protein?"

Speaking strictly for myself, I assume that protein is being metabolized both from damaged cells and dietary sources, if available. I also operate on the assumption that very little tissue repair takes place while exercising, and also that protein is less efficient as an energy source due to the necessity of removing its nitrogen before feeding it into the Krebs Cycle. As a result, I use Hammer's protein proportion in my homemade Perpetuem and save the majority for my evening meal, when it is more likely to be efficiently used for tissue repair. Most commercial recovery drinks seem to operate on this assumption, too.

"Would added protein inhibit fat utilization?"

I don't know.

"Once again, I am assuming that the protein you ingest the rest of the time — while not actually hiking — is a Good Thing, but not related to the use of protein for energy during the hiking day."

It is related only in the sense that it is put to better use while resting. Also, the high amount of heat produced by metabolizing protein is better put to use warming your sleeping bag/quilt than being flared off during the day and possibly contributing to hyperthermia.

“If you want to optimize for no protein catabolism, you need moderately high protein and high calories, with not too much from fat.
If you want to optimize the weight of your pack, you need to go for high fat.
As far as I can tell, there’s no way to optimize along both dimensions simultaneously.”

As far as I can tell the story is:

* There will be some unavoidable muscle catabolism during strenuous or prolonged exercise.

* The amount of catabolism is not great, and suitable post-exercise nutrition will reverse this resulting in a net positive effect on the working muscles. A good recovery drink, containing protein, helps.

Here is a discussion that sounds pretty reasonable to me

–MV

"Any idea how the percent protein utilized for energy varies, such as with exercise intensity? I'm still trying to understand the apparent discrepancy between the protein they provide in their drink and what they say the body uses."

Bob-As Greg advises, I would read what Hammer says with a certain amount of caution. I have yet to see a disinterested, scientific source that does not use a constant of 5% protein as an energy source, without regard to exercise intensity.

I have been reading around today, and I have found the 5%-15% value elsewhere as well. That place stated the higher values could occur in high intensity exercise without enough carbohydrate.

It sounds to me as if the higher protein consumption should be nothing to worry about for anything but extreme (intensity or duration) backpacking, and even then mainly if you do not use enough carbohydrate.

–MV

"Typically, I can go for about two weeks with 3000 cal/day intake. During that time, I'm losing about 1/2 pound/day when I'm doing 20-25 mile days. Most of that's fat (by various criteria), but a small amount is almost certainly coming from catabolism of protein……Probably on order of 5000 calories/day."

If your 5000 calorie estimate is accurate, the results are consistent. 3000 calories from dietary sources plus 1750 calories of body fat plus protein catabolism = 5% puts you very close to 5000 calories.

Some sources for the relation between endurance training and fat utilization as a substrate. The first is a good general overview; the others are more narrowly focused. I hope they help. What I would really recommend is reading the relevant chapters of "Exercise Physiology Energy, Nutrition, and Human Performance" by McArdle, Katch, and Katch. They really get into the nitty gritty of how the various substrates are used under various conditions in the early chapters. I've got the 6th Edition, published in 2007, but I think there's a new one on the market(and in libraries) now. What I have looked at is way too complex for a Forum post, so all I'll do here is point you to what I consider an excellent source. The authors are serious scholars.

http://www.unm.edu/~lkravitz/Article%20folder/limitations.html

http://www.ncbi.nlm.nih.gov/pubmed/9781322

http://www.gssiweb.org/Article/sse-59-fat-metabolism-during-exercise-new-concepts

http://www.ncbi.nlm.nih.gov/pubmed/17414804

"If you want to optimize for no protein catabolism, you need moderately high protein and high calories, with not too much from fat.

If you want to optimize the weight of your pack, you need to go for high fat.
As far as I can tell, there's no way to optimize along both dimensions simultaneously."

I am pretty certain that you can optimize the weight of your pack for shorter trips by providing adequate carbs to support the metabolism of both dietary and body fat. Tissue catabolism is a tougher nut to crack, because you have to not only provide enough protein, but also make sure it has the correct amino acid profile. Easier said than done, although whey and egg protein come close out of the box. It's why I use whey in place of soy.

Longer trips are much tougher to plan for in both regards, because you will no longer be able to utilize body fat to any significant degree, and what might have been tolerable tissue catabolism on a short trip could turn out to be a major problem on a longer hike. McArdle's "Exercise Physiology" maintains that fat utilization at lower levels of exercise intensity can exceed 80% in well trained athletes, which is worth
taking note of when planning your approach to training. One of the implications is that you could allocate a higher percentage of your carried food to fat sources and protein, because you would require less carbs as an energy source. IF you were hiking at a lower level of intensity relative to your VO2 max.

"Tom suggested that might be about 10%. Whether or not he is exactly correct, I believe that is in the ballpark. It is also leaner than most of us are."

I was erring on the side of caution. The real limit is probably lower. I think RJ mentioned something like 8%, and I raced in my early 40's at a weight of 132# and body fat that had to be around 6%, if that, and did just fine for several years. I'd be too embarrassed to post a picture of what I looked like. But how low anyone would ant to go has to be a personal decision. I figure it's better to play it conservative in the mountains, simply to have something in reserve for unseen contingencies.

Other than that, +1 to your whole post.

"Here is a discussion that sounds pretty reasonable to me"

Excellent article, Bob! It looks like their findings correlate with Hammer's on protein/carb ingestion during exercise, as well as the general recovery drink protein amount. This is one of the most useful articles I have read in a long time. Thanks!

I also enjoyed the article very much, thank you for the link.
One bit of experimentation that I did on myself this summer during my PCT thru hike was to use a mixture of tsampa, nuts, seeds (chia, hemp and flax) and proteins in the form of various meat jerkies and dehydrated beans PLUS fats like olive and coconut oils. Usually in the mornings I added some dehydrated fruits to the mixture for a sweeter taste. I could mix the ground roasted barley plus the other stuff as a pemmican or prepare it as a soup depending on how much water I had available. I ate this morning and evenings, snacking the rest of the day. While not a very attractive looking food source I did find it very sustaining. My purpose was to find a better way to utilize the food weight I was carrying and see just exactly how my body reacts to the injestion of roasted barley flour as I had formerly been using oats, corn, beans and jerkies and some foil packed fish for my carb and protein needs and was getting tired of that. I found the Tsampa flour to be a pretty versatile base food source and I did pretty well on it through a cold wet Washington finish and maintained my weight at a steady 15-20 mile per day pace.
I got back home and saw on the Patagonia site they are now selling Tsampa as a food source for outdoor activities…….go figure.:-/

""Here is a discussion that sounds pretty reasonable to me"

"Excellent article, Bob! It looks like their findings correlate with Hammer's on protein/carb ingestion during exercise, as well as the general recovery drink protein amount. This is one of the most useful articles I have read in a long time. Thanks!"

Indeed. Nice find. This looks to me to be a reasonably well-balanced, thoughtful review. FWIW, it was subsequently published in symposium edition of Sports Medicine. You can find it online (see the acknowledgments for sponsorship info, etc.).

Interestingly, the abstract of the author's original peer-reviewed published work on protein/carb ingestion during exercise ends with "We conclude that muscle protein synthesis is stimulated during continuous endurance type exercise activities when carbohydrate with or without protein is ingested. Protein coingestion does not further increase muscle protein synthesis rates during continuous endurance type exercise."

Looking at the data, I think he might appropriately have written "does not cause a statistically significant further increase…" That's what they found when looking directly at the vastus lateralis. Whole body did show statistically significant differences.

Cheers,

Bill S.

Okay, I'm not the most savvy person nutrition-wise. Nor am I a top level athlete. I'm interested in ensuring that I efficiently get what I need to hike 25 mile days. Currently I do 20's and am working towards 25's.

At home it's: Don't worry so much about the fats, just make sure you get a lot of veggies.

On the trail it's: who cares what I eat so long as it's mostly carbs in the day and heavy with protein and fats at night–I'm thinking warmth and restoration.

So when I read the statement below my general trail food practice seems to be in the correct direction. Or am I not understanding something?

> "Protein coingestion does not further increase muscle protein synthesis rates during continuous endurance type exercise."

"I have yet to see a disinterested, scientific source that does not use a constant of 5% protein as an energy source, without regard to exercise intensity."

Tom, I'm not sure I understand what you mean by this statement. Can you clarify? Sources helpful if it's easy for you to put your finger on them.

Thanks!

best,

Bill

"Tom, I'm not sure I understand what you mean by this statement. Can you clarify? Sources helpful if it's easy for you to put your finger on them."

Bill-I first ran across it in Richard Nisley's posts and the table he supplied. Later, I ran across it in McArdle's tome, "Exercise Physiology…….", to which I supplied a link in a previous post, in his discussion of how to determine the percentage of fat or carbohydrate being metabolized from exhaled air. The McArdle edition I was reading then was the fifth edition, and protein was assigned a constant value of 5%. I just went back are re read the section in my sixth edition, and protein is no longer assigned a constant value, as they have developed a way to measure protein metabolism by correlating the amount of nitrogen excreted in the urine
with the results of the exhaled gas analysis. However, the standard tables used to determine the ratio of carbs to fat during exhaled gas analysis do not take protein into account because its exclusion results in minimal error, due to the small amount of protein typically metabolized. If you'd like to read the explanation in detail, start on page 191 of "Exercise Physiology…" by McArdle, in the 6th edition. If you look at later or earlier editions, look for the section on Respiratory Quotient, where it is explained in great detail. In any case, the 5% protein constant has been replaced by a more refined approach, where protein metabolism percentage can now be calculated, but is generally not, because it is so small as to be insignificant.
That said, I stand corrected, as the constant I quoted has been superceded by new techniques. The standard, however, remains the same, in that protein is assumed to be an insignificant source of energy in the vast majority of cases. I hope this helps. Assuming the new techniques are accurate, protein would seem to supply even less than 5% from what they seem to be saying. If you decide to follow up on this, I would be interested in your take on the matter.

Tom

Edited to address the right poster. My apologies, Bill. It was late, for me, in the
evening, and I'm just getting over a cold.

Edited again: I finally located the 5% figure for protein as an energy substrate. It is in an earlier chapter of McArdle, et. al., which gives a figure of 2-5% for a well nourished individual at rest. The figure increases with exercise in general, and even more so if there is a shortage of glycogen. It is stated, based on new ways of measuring nitrogen excretion, that protein plays a larger role as an energy source than previously thought, although small compared to carbs and fat barring extreme conditions.