Hi,
I was reading with interest the exchanges on long-distance hiking diets and nutritional needs. A few members commented that one could factor in about 3500 calories in existing body fat per day, assuming that one has the fat to lose. ASSUMING a 4500-5000 calorie diet per day, and a hiking style that mostly burns fat (i.e. 80% fat, 15% carbohydrates and 5% protein)that would leave me with only 1500 calories in food to take, of which most would be carbohydrates and protein. That seems very little to me ...
I did ask a specialist and got the following answer:
"I wouldn't agree generally, unless hiking in extreme conditions without food. The body will utilize incoming food, but draw on stores--fat and carbohydrate . About half and half for the first few weeks. If you are losing a few pounds each day, it implies glycogen and fat stores are getting low. (Muscle glycogen is the first to go--about 4 pounds weight loss.) After Muscle glycogen, liver glycogen is released by order of the brain, to nourish it. Avoid depleting liver and muscle glycogen by resting and snacking often. Fat will burn off slower, but steadily. If you are "pushing" too hard with too little food, your muscles (protein) will be shrinking as you burn them up. To lose 7 pounds in one week probably represents 3 pounds of water loss, 1 pound of muscle glycogen, and 3 pounds of fat. No, it is not a healthy diet".
Any more insights on using exisiting body fat and how much to factor in?
Thanks!
Sven

If you are losing a few pounds each day

Who is talking about losing a FEW pounds each day? We are talking about losing 1 pound per day.

It implies glycogen and fat stores are getting low.

Fat stores are NOT getting low anytime soon. Glycogen stores will get low if we burn them off too fast. We have to go slow to avoid this.

Muscle glycogen is the first to go--about 4 pounds weight loss.

ONLY if we go too fast. We must be very careful NOT to stress our muscles so as NOT to burn glycogen rapidly.

After Muscle glycogen, liver glycogen is released by order of the brain, to nourish it.

The brain is another story. There is nothing we can do to reduce our brain's requirement for 600 calories or so a day of glucose, which is why we can't live on a mostly fat diet as some foolishly suggest.

Avoid depleting liver and muscle glycogen by resting and snacking often.

This is partly true with respect to liver glycogen. As I noted above, what is used by the brain must be replaced from food intake, otherwise we will burn muscle. With respect to the muscles, the correct way to avoid depletion is to SLOW DOWN and thus burn mostly fat.

As for resting, that is irrelevant. Resting doesn't rebuild glycogen stores--eating food rebuilds glycogen stores. And there is no difference in calorie consumption between walking slowly but steadily without stops and walking slowly but steadily with occasional stops. Then again, if you want to rest, by all means rest. The important thing is to walk slowly so as to avoid burning glycogen.

As for the business of eating often, the scientific basis for this is that we want to avoid blood sugar to spikes, since this will cause insulin to be released and may cause precious carbs to be converted into fat. To avoid this, eat low-glycemic index foods, such as plain rolled oats. Avoid easily digested sugars.

Fat will burn off slower, but steadily. If you are "pushing" too hard with too little food, your muscles (protein) will be shrinking as you burn them up.

Finally, the good doctor says something intelligent. This is just what I have been repeating over and over. You must go SLOW to burn fat. Otherwise, you will burn glucose until you run out of glycogen reserves, at which point you begin converting muscle protein to glucose.

To lose 7 pounds in one week probably represents 3 pounds of water loss, 1 pound of muscle glycogen, and 3 pounds of fat. No, it is not a healthy diet".

Now the doctor has changed his mind. He is talking about losing 1 pound per day, just as we originally agreed. Water loss is irrelevant. The loss of muscle glycogen is serious. This loss implies we were walking too fast. We need to slow down to avoid this. At 1700 calories/day of food intake (a pound of oats mixed with non-fat dried milk to boost protein percentage and reduce fat percentage), of which 1200 is carbs, 300 protein and 200 fat, we must devote 600 carbs to the brain and that leaves only 600 carbs for the muscles, with the muscles burning 3500 calories/day of fat (this implies 15% glucose, 85% fat).

The doctor sounds like he is knee-jerk reacting to the same question he has been asked umpteen times by fat and lazy middle-aged slobs who want to continue to feed their faces constantly but lose weight at the same time. "No, you can't lose weight fast." The doctor simply can't conceive of the concept that someone is actually doing slow but steady exercise for 8 to 10 hours/day like our ancestors used to do. This is something unheard of in the modern world, after all. Either you sit on your ass watching the tube all day, or you rush through some super-stressful routine at the gym. One extreme to the other.

Again, in order to get past the hysteria, I suggest you reflect on how our ancestors lived and how primitive peoples live today. Feast-famine is the norm in nature, so how is it that we humans managed to survive this long if we aren't well adapted to feast-famine?

Alternatively, read this trip report http://www.golite.com/team/athletes/coup/ct_report.pdf by the guy at Golite. At the end of this trip report, he notes that he lost 1.25 pounds/day by walking slowly but steadily. How does the doctor explain that?

If you read this report closely, you'll see that this guy ate approximately 1 pound of food/day (he planned on 2 lbs per day, but a bunch of food spoiled and he had some left over at the end). His food choice was very poor: dried fruit, which has a high glycemic index, and nuts, which are mostly fat. He was probably lacking to 50-100 grams of protein that we need to repair tissues. A much better choice would have been plain rolled oats, with a little non-fat dried milk mixed in to boost protein and reduce fat percentages, and preferably eaten raw, so as to reduce glycemic index and also save the weight of a stove and fuel.

Edited by frprovis on 02/28/2006 10:21:58 MST.

Thanks Frank for your lively contribution :-) Do you know if computed energy needs based on weight, distance and terrain usually include the 600 carbs that we need to devote to the brain or is that to be added on? In addition, what is your take on gradually getting the body used to dipping into its fat reserves before going on a longer trip by gradually reducing the calorific intake over a period of 1-2 weeks? (I personally do not hike 8-10 hours on a daily basis before going on trips). I hear that reducing your intake too abruptly may lead to a "hunger mode" which would impede the process of using stored fat reserves. (?)
Thanks!
Sven

Do you know if computed energy needs based on weight, distance and terrain usually include the 600 carbs that we need to devote to the brain or is that to be added on?

No, I don't know. Anyway, the whole business of how many calories we need to do a given amount of work is completely unscientific. You can waste energy by moving inefficiently, or you can conserve energy by moving gracefully. Basal metabolism can vary for all sorts of reasons. Take all calorie estimates with a huge dose of skepticism.

In addition, what is your take on gradually getting the body used to dipping into its fat reserves before going on a longer trip by gradually reducing the calorific intake over a period of 1-2 weeks? (I personally do not hike 8-10 hours on a daily basis before going on trips). I hear that reducing your intake too abruptly may lead to a "hunger mode" which would impede the process of using stored fat reserves. (?)

I'm not sure there is any scientific basis for what you are describing. In any case, even if there were a scientific basis, it would be shaky because there is no way to run double-blind experiments about this sort of thing. Here is what you can do:

First, you can control your mental response to hunger by regularly going without food so you don't panic at the notion of suffering from a little hunger. For example, you can practice eating just one huge meal a day, in the evenings. This will cause you to feel hungry in the afternoon. After a while, you'll start to enjoy this hunger, becuase it means the evening feast time is approaching. This hunger will NOT cause a drop in energy, assuming you haven't messed up your blood sugar somehow (such as by eating too many high-glycemic index foods during your previous evening feast). I have been eating one big meal a day for years now, at least when I am at home. (I don't work anymore, so my feast is a lunch feast. For people with jobs, an evening feast is much better.)

Second, you can learn to move gracefully and try to carry this gracefulness with you while hiking, so that you don't stress yourself out and thereby burn precious muscle glycogen. This is also mainly mental training. There is no one way to achieve this gracefulness.

Third, you can develop your hiking muscles sufficiently that you are able to hike uphill, with a pack, without burning too much glycogen. The way to do this is obvious. Namely, practice hiking uphill with a heavy pack. Since you probably don't want to practice 10 hours a day, just put on a very heavy pack and walk up a very steep hill for a much shorter period of time.