I am in the process of trying to optimize my backpacking diet for the Nth time and am interested in any and all comments, advice, etc.
Assumptions
1) I weigh ~137# and usually add ~5#
of body fat gradually over the month
before long trips (10-12 days in my
case).
2) Pack weighs ~ 30# and clothing worn
3.5# for total weight of 175.5#
(the weight I use to calculate
calorie expenditure).
3) I use a calorie expenditure
calculator with backpacking as the
activity and a weight of 175 to
get a calorie estimate of ~ 4450.
4) My food yields ~2925 calories/day
with 1440 cal from carbs, 308 cal
from protein, and 1177 cal from
fat.
This leaves me with a calorie deficit of
~1525 calories to derive from body fat,
which equals ~ .44# of body fat, sufficient to make up the deficit for 11 day plus a little. This diet tries to replace most of my glycogen on a daily basis, provide enough protein for body repair with a little in reserve for gluconeogenisis if I exhaust my glycogen, and provide as many calories as I can from dietary fat with the remaining weight.
I would greatly appreciate feedback.

Tom-A unit of metabolic equivalent, or MET, is defined as the number of calories consumed per minute in an activity relative to the basal metabolic rate (BMR). A single unit (1 MET) is the caloric consumption of that individual, while at complete rest, aka BMR. For example the restful state following a quiet night's sleep is a single MET. Hiking cross country, or backpacking, averages 6 MET with an adequate diet. Burning fat, carbohydrates and proteins is referred to as substrate utilization. Your planned substrate utilization is 32% CHO, 61% fat, and 7% Pro.

For any 6 MET sport, which lasted about an hour or less, your actual substrate ratio utilization would be ~ 39% CHO, 56% fat, and 5% pro. After about 3 hours at 6 METs, your substrate utilization should have shifted to burn at least 10% more fat. Your planned substrate utilization looks fine.

I used the mean values for endurance athletes in the above brief analysis. They have a rough bell curve distribution of substrate utilization ratios. It starts with rest and persists during exercise of increasing intensity. The major determinants of resting "respiratory equivalence ratio" (RER) are: muscle glycogen content, training volume, proportion of type 1 fibers (slow twitch), FFA / lactate in your blood, and % dietary fat intake. This is a long winded way of saying, "Only taking an RER test will result in 100% accuracy for your planned substrate utilization."

Edited by richard295 on 11/06/2006 23:39:16 MST.

Richard - When referring to CHO do you mean carbohydrates?

Edited by sharalds on 11/06/2006 14:21:47 MST.

Sam-Yes

Hi Richard,
Many thanks for the really informative beta. You have pushed me further along a path I was just starting out on. For years I have pretty much adhered to the approach taken by Ryan, Roman, and Jason for the Arctic 1000 trek and it served me decently for the longer trips of my younger days-in the 16-17 day range. But I was carrying much heavier loads then and calories, not speed, was the issue. More recently, as I moved in the direction of lightweight, if not ultra light, backpacking, I began to up the percentage of CHO in my diet, but was never sure how far to take it because as CHO increases, either calories decrease or weight increases with all that implies in terms of limitations on trip duration, pack weight, etc. So, it was pretty much trial and error. You have given me a much clearer idea of the tradeoffs involved in terms of CHO percentage and pace which will come in especially handy for some PCT section hikes I am contemplating, where a faster pace is required if one is to cover the distances involved in a practical timeframe. Heretofore the type of backpacking I have done-mostly off trail wandering-rarely put me much above the 4 MET range except for booking on out the last day or two. Never had much trouble making it back to the car, BTW. Guess it was that pot of beer I visualized at the end of the
rainbow:-)...

Tom-I recalcuated the numbers and discovered I screwed up on my original post yesterday. I went back today and corrected the original post numbers. I shouldn't have checked my numbers before I posted them the first time... sorry.

Sam,

Richard already answered you. I'm only adding, IIRC basic biochem (i don't trust my memory any longer; some of the simplest things i forget), CHO is used since carbs (whether simple sugars or starches) are composed of only three elements C[arbon]-H[ydrogen]-O[xygen] in varying combinations and arrangements, hence CHO. Just thought someone might like to know. Furthermore, amino acids add in nitrogen, and some also have sulfur (and we all know what happens if many of the sulfurous AA's are consumed). This is why, in some fields (e.g. Microbiology) carbs are spoken of as a carbon source, and AA's as a nitrogen source (just two of several basic requirements for culturing nearly all bacteria). Someone might, from time to time, also hear the terms "carbon source" and "nitrogen source" - hence, my explanation of those terms also.

Edited by pj on 11/07/2006 02:38:53 MST.

Hi Richard,
Thanks for being so conscientious. I really appreciate all this feedback. While we're on the subject, could you tell me how the ratio would shift if I were to drop back to a 4 MET level of output(~2.5 mph), which is the level I would probably shoot for if I were trying to extend my trip out to,say, 18 days, i.e. the kind of trip where I just wanted to get out there and wander around without any "balls to the wall" agenda? My sense is that I would up the fat percentage a la Arctic 1000, but it would be nice to hear your perspective on the subject.

Another point. If I'm on the right track, would I also want to pack another 2.5-3# of lard around my middle?
i.e. ~.44# per day x 6 additional days?

I will address your last question first. Don’t “…pack another 2.5-3# of lard around my (your) middle”. You will get 3,500C from every fat pound around your middle and 4,000C from every fat pound in your pack.

Now I will address your first question. For a male, (estimated age of 30), (estimated height value of 69”), (estimated VO2max category of Very Good), bulked up from 142 to 147 lbs, 5 lbs of clothing worn, and an average pack weight of 30 lbs your approximate energy requirements are shown in the attached data grid. I created it for your unique parameters. Ignore the negative numbers in the grid, that’s a bug I need to fix. Interpret any negative number as equal to the last prior positive number

Your body will shift over from the non endurance ratios to the endurance ratios at the approximate rates shown in the attached chart:



Your unique backpacking METs are as follows:
4.0 MET - Walking at 4 mph without your 35 lb pack
5.0 MET – Walking at 4 mph with your 35 lb pack

To achieve 4 MET with your pack, you have to drop your speed to about 2 mph.



Look at the 3.9 MET row and you will see that for the first 4 hours the CHO requirement is 79%. For the next 8 hours, of a 12 hour hiking day, the CHO requirement is 21%. The fat is ramping up as the CHO is ramping down during the first 3 hours. The ramp up average of the 79% after 30min and the 21% after three hours is 50%. (4/12)*0.50 + (8/12)*0.21 = 31% CHO. You are currently planning on bringing 32% CHO. This is right on the knife edge for 4 MET. If you try and up your pace past 4 MET, the CHO requirement will prevent that from happening. Bringing any additional fat% is counter productive. You won't be able to burn any extra fat unless the CHO is also upped to the requirement for the MET. Remember that fat only burns in a CHO fire.

The pace that I like to keep on my backpacking trips keeps me in the 6 - 8 MET range. Obviously this results in a much larger CHO% requirement. The downside is that my food calorie density is not as high as yours.

Disclaimer:
This topic is highly complex and very controversial. Even among the "experts" the data is often interpreted differently from one researcher to another. What is presented here a compilation of information from several text and current scientific journals into what I hope is an easily understandable format but without the hyperbole of the mainstream media.

Edited by richard295 on 11/08/2006 22:22:42 MST.

Thanks again, Richard. The charts give me a lot to think about in terms of substrate allocation as I plan my menus
for various types of trips. I am assuming that Fat, CHO, and PRO are expressed first in calories, then in percentages, PRO % being derived indirectly. I am not familiar with the PMV and P MV notations. However, the chart makes a lot of sense even without understanding them. One further line of questioning: Up until now, I have structured my daily food intake to emphasize fat and protein intake at my evening meal to avoid competition with the working muscles during hiking hours. During the day I use mostly high CHO liquids such as Hammer's Perpetuem and EFS's E3. The former is maltodextrin based with some soy protein isolate and lecithin, whereas the latter uses glucose, a good dose of electrolytes, and ~ 6 grams of amino acids(glutamine,valine, leucine, iso-leucine). Both seem to work very well for me when I'm on the move. I assume that when I stop hiking there is some sort of reverse curve in substrate utilization in the direction of a return to my basal metabolic rate, modulated by the need to repair tissue damage, replenish glycogen stores, burn off any accumulated lactic acid, among other things. So, the first thing I do when I stop is mix up a pint of EFS's Ultragen, which contains 60 grams of glucose, 20 grams of whey protein isolate, electrolytes, some vitamins(mostly B complex), and 6 grams of glutaime. The logic here is to get a headstart on glycogen replenishment while the muscles cells are particularly receptive(within 1/2 hr of ceasing exercise is my understanding). Then I set up camp and finally get down to serious eating-heavy on fat but with ample protein and carbs. The idea is to let the main thermogenic process unfold overnight, while I am at rest, creating no competition with the working muscles
and giving the added benefit of using the heat generated to warm my sleeping bag(and me). I like to think of it as putting entropy to good use. Does this approach make sense to you? Again, in the absence of any formal training, I'm sort of feeling my way, based on perusing some exercise physiology texts
along with a healthy dose of trial and error with me as the guinea pig. Another dietary idea I would like to run by you: The higher one goes, the more CHO should be used as a substrate to maintain the same performance level.
The reasoning is that O2 varies inversely with altitude and CHO metabolizes completely with less O2, i.e. 1 C6H12O6 + 6O2 = 6 CO2 + 6 H2O = an exchange ratio of 1. As I understand it, the ratio for FAT and PRO is considerably less favorable,
although I can't remember the exact numbers, something like . .8 for a typical fatty acid and .7 for a typical amino acid, plus extra water to get rid of the urea resulting from PRO catabolism. Am I sort of in the ball park here. It impacts how I structure my menu because I spend a lot of time above 12000' and there days when I know I will be going higher than that with some miles to cover. Should I consider upping the CHO % in my meals for those days?

I want am not formally trained in physiology. Most of my knowledge comes from having prepared for numerous expeditions. Secondarily, I am also doing some related research for my business start-up. With that caveat I will answer your questions.

PMV –
This is just the acronym I assigned to a class of regression formulas I used for the calculations. What is most relevant is what’s specified at the end of the label. PMV C/hr is the Calories per hour you will be burning. PMV C/hr M is your personal METs value for that level of energy expenditure.

During and immediate post endurance exercise nourishment requirements –
Both your exercise nutrition strategies are sound. Rates of glycogen synthesis may be nearly two times faster than normal in the first two hours after a workout. After this two-hour time window, the rate of glycogen formation returns to normal levels. Your immediate post exercise CHO/Pro ratio is now 3 to 1. Theoretically 4 to 1 is the optimal ratio.

Thermogenic process-
Yes but it is the protein, not the fat, that will most help keep you warm at night. Diet induced thermo genesis (DIT) is different for each nutrient based on the amount of ATP required for the initial steps of metabolism and storage. Fat is 0-3%, CHO is 5-10%, protein is 20-30%, and alcohol is 10-30% <grin>.

Altitude impact on CHO requirements-
At higher altitude, the partial pressure of oxygen is lower than at sea level. This results in the relative contribution of anaerobic glycolysis to ATP production being increased and muscle glycogen stores more rapidly depleted. Relative work intensity (% VO2max) or METs (% VO2 / %VO2max) is the main factor determining fuel selection during exercise. In other words, you can get around this problem by just maintaining your target MET level by reducing your exertion rate.

Edited by richard295 on 11/09/2006 21:29:31 MST.

My backpacking food philosophy is to simply find foods you don't easily tire of and don't go hungry. Unless you are doing multi-week hikes, I see no purpose in doing more than that.

John-I agree with you. I only go through this type of food planning exercise for my multi-week expeditions.

In my case that is at least once per year for trips averaging 6 weeks in duration; most importantly I need to keep pace with some gifted athletes on the expeditions; I need to have my food purchased and shipped to my drop destinations up to a month in advance; I can only reach one of my pre-shipped food drops about every two to three weeks; and the food volume has to be small enough that I can both carry it and store it in bear resistant containers.

The only other two situations, that I can think of are; if you plan to, or are now competing, in adventure races or; if optimizing all aspects of your pack weight is enjoyable for non-multi-week trips.

Edited by richard295 on 11/10/2006 05:53:50 MST.

"unless you are doing multi-week hikes, I see no purpose in doing more than that".
From my perspective, whether the hike is one day or multi-week, the principle is the same: Select your food to support the expected level of exertion you will be asking of your body. To do that, one has to understand how the mix of substrates utilized by the body varies with the intensity of the effort.
On longer trips the emphasis shifts inexorably in the direction of reduced
effort(pace) as the calories utilized will increasingly come from fat due to space considerations in one's pack. At least that has been my experience and, apparently, all the guys on the Arctic 1000. Even so, as Richard points out, fat burns in a carbohydrate flame so there always has to be a minimal amount
of CHO in the mix. On a less directly practical level, I derive a lot of satisfaction from tinkering with my hiking diet and watching how my body responds in the field. When I get it right for a given set of conditions, I'm about as close to nirvana as I'm likely to get in this life. But that's just my personal journey. Thanks to you all for contributing to my education
on this thread.