There is another thread about ultra light food, which within the bounds of palatability suggested that there are more calories per gram in fat than anything else and that roughage and water have no calorific value. This leaves food like chocolate and nuts as optimal while you can stomach them.
Above 10,000 feet up funny things happen, and people loose appetite and then weight and can get altitude sickness. Altitude sickness is not totally understood. I have been reading that fat metabolism consumes more body oxygen per calorie than carbohydrate metabolism. There may be a connection between a high fat diet and increased altitude sickness. Optimum UL diet at altitude may well be less fatty than at sea level.
No one seems to be able to prove any of this this. What do people think?

ref http://www.bodyresults.com/E2HighAltitudeNutrition.asp

Edited by Derekoak on 05/29/2008 07:26:13 MDT.

What is the definition of ultralight food?

good question to which I expect there are many answers. I would suggest as a start, a diet of minimum weight per day that allows the body to hold muscle mass whilst walking all day. At altitude in addition to avoid altitude sickness if it is diet related

Edited by Derekoak on 05/29/2008 09:26:56 MDT.

Hence why I eat a LOT of easy to digest carbs and fiber in my diet, no matter where I go in hiking. Yes, a diet of nuts and oils would rule in carrying small amounts of food (keeping weight down) but it isn't an easy diet to maintain.

Hi Derek. happy to see some discussion started on UL food.

My suggestion would be to term anything thats 130+cal/gm as UL. (that way I can include ramen cup noodle in my food and still boast of being truly UL)

curious to what others have to say.

I am not sure whether the effects start as low as 10,000', but certainly above 4,000 metres it starts to get harder to digest fats. Above 5,000 m I found sugars and carbos were OK, but not fats at all.

I don't know about a connection between a high fat diet and increased altitude sickness, but there is meant to be one between low liquid intake and altitude sickness. Maybe a high fat diet causes reduced appetite and hence reduced liquid intake?

But very often high altitude just causes reduced food intake through fatigue, and that can be a serious problem. How often do you read something like 'too tired to cook or melt water so went to sleep'?

Cheers

Although I'm sure the higher altitudes have much more pronounced effects, I definitely experience the effects of digesting fats much lower. Even at an 8,000 foot ski town the alfredo sauce doesn't digest right.

Several years ago my wife and I did a weeklong trip in the Sierra, with elevations generally 10,000 to 12,000 feet ending up at 14,500 feet on the last day. We had set up our lunches with things like Powerbars some days, GORP (raisins, peanuts, M&M's) and jerky others.

There was a noticible difference in energy levels and sleepiness between these diets. More fat made us slower and sleepy. From that experience I learned to try and keep the mid-day foods mostly carbs with limited fat and protein. Dinner can have more fat and protein.

Regarding "ultralight food" in general I think it depends on the sort of trip and your physical condition. The longest sustained hike I've done was 16 days, more commonly I have done roughly a week. I carry a good 10 pounds of fat that I'd be happy to burn up.

For me, on fairly short trips, it makes sense to eat in a manner that allows use of body fat. For the most part this means keeping effort well down in the aerobic area and providing a steady flow of carbs as "kindling" to help burn body fat. So even though fat has double the calorie density of carbs, if I can leverage a pound of stored body fat with 6 ounces of carbs I'm way ahead.

I recently heard a podcast interview with Demetri Coupounas of GoLite. He talked about subsisting primarily on about a pound of dried mango with just enough fats (nuts I think) added to keep his body from going into famine mode. Made a lot of sense to me.

Edited by jimqpublic on 05/30/2008 12:06:29 MDT.

1. Your body preferentially burns carbohydrates over fat when available. Supply more energy than you expend in the form of dietary carbohydrate intake and you will never tap into body fat reserves. In fact, dietary carbohydrate intake in excess of energy needs ends up *as* adipose tissue.

2. You do not need carbohydrates to kindle/burn body fat. Appreciable amounts of body fat are only burned for fuel (activation of lipolysis) once glucose/glycogen stores have been depleted. If you *needed* dietary carbs to burn fat, nary a pound would've ever been lost by those following the low carbohydrate way of eating.

ETA: In (1) above, I should've been more specific versus relying on the general catch phrase "dietary carbohydrates". Kind matters.

Edited by fetch on 05/31/2008 11:27:56 MDT.

The problem is that for a number of people a high fat diet leaves little to be desired. I know often all I can stomach at high altitude is soup - filled with simple carbs and protein and maybe a drizzle of olive oil. I feel incredibly sick if I eat just nuts or a pack of tuna for lunch when in alpine. Part of it is....I just need time to digest those foods and when hiking I don't have the luxury of a nap for an hour!

Fetch,
Sounds to me like you skipped Physiology 100. What you have posted is at odds with any exercise physiology text I have ever come across. I will refer you to the one I keep around as a reference: Exercise Physiology
Energy, Nutrition,
& Human Performance
6th edition
The authors, William D. McArdle, Frank I. Katch, and Victor L. Katch all have pretty impressive credentials. If you read through the text you will find that the body actually burns a mixture of carbs, fat, and protein at all times, the ratio of carbs to fat determined by the intensity of the exercise, with protein held relatively constant at ~5% under all but extreme circumstances.
Further, carbohydrate is indeed required for fat metabolism, hence the axiom "fat burns in a carbohydrate flame". But don't take my word for it. Go read what some real experts have to say. Any standard college text will tell you pretty much the same thing, but the text I mentioned above wouldn't be a bad place to start.

Tom:

1. Because I'm "at odds", as you say, the conclusion drawn is I am the one who is erring. Interesting.

2. Carbohydrate flame? More like amino acid flame.

3. A 2006 publication date is the literary equivalent to the Dark Ages when it comes to such things.

4. Sure, for the SAD. Being overly simplistic, if there is no physiologically significant carbohydrate available what happens? Your metabolism doesn't grind to a halt. You certainly don't die. You switch over to lipolysis (and to a lesser degree, gluconeogensis) to maintain homeostasis. Don't fear the ketone.

5. "Credentials" only matter to those claim them and the people who believe them. "Experts" are a myth.

6. College? :o)

I'll stop there to prevent this thread from diving deeper into the weeds than it already is. I didn't mean to upset your apple cart of mammalian physiology, biochemistry, endocrinology and dietary/nutrient metabolism interpretation/understanding. Especially since there are people far more qualified than I who would still fail to convince you otherwise. You've already established that in no uncertain terms (see 1 above). As such, it would be pointless to engage you further on the topic as we both know we're right.

Regards,

fetch

Edited by fetch on 05/31/2008 11:28:46 MDT.

Metabolic Interrelationships (pdf file) Medical Biochemistry from Univ. of Illinois at Chicago

Exercise Physiology

Fuel usage

Fuel usage (light exercise)

The best examples of light exercise are walking and light jogging. The muscles that are recruited during this type of exercise are those that contain a large amount of type I muscle cells, and, because these cells have a good blood supply, it is easy to for fuels and oxygen to travel to the muscle. ATP consumption makes ADP available for new ATP synthesis.

The presence of ADP (and the resulting synthesis of ATP) simulates the movement of hydrogen (H+) into the mitochondria; this, in turn, reduces the proton gradient and thus stimulates electron transport. The hydrogen on the reduced form of nicotinamide adenine dinucleotide (NADH) is used up, nicotinamide adenine dinucleotide (NAD) becomes available, and fatty acids and glucose are oxidized. Incidentally, the calcium released during contraction stimulates the enzymes in the Krebs cycle and stimulates the movement of the glucose transporter 4 (GLUT-4) from inside of the muscle cell to the cell membrane. Both these exercise-induced responses augment the elevation in fuel oxidation caused by the increase in ATP consumption.

Fuel usage (moderate exercise)

An increase in the pace of running simply results in an increased rate of fuel consumption, an increased fatty acid release, and, therefore, an increase in the rate of muscle fatty acid oxidation. However, if the intensity of the exercise increases even further, a stage is reached in which the rate of fatty acid oxidation becomes limited.

The reasons why the rate of fatty acid oxidation reaches a maximum are not clear, but it is possible that the enzymes in the beta-oxidation pathway are saturated (ie, they reach a stage in which their maximal velocity [Vmax] is less than the rate of acetyl-coenzyme A [acetyl-CoA] consumption in the Krebs cycle). Alternatively, it may be that the availability of carnitine (the chemical required to transport the fatty acids into the mitochondria) becomes limited.

Whatever the reason, the consequence is that as the pace rises, the demand for acetyl-CoA cannot be met by fatty acid oxidation alone. The accumulation of acetyl-CoA that was so effective at inhibiting the oxidation of glucose is no longer present, so pyruvate dehydrogenase starts working again and pyruvate is converted into acetyl-CoA. In other words, more of the glucose that enters the muscle cell is oxidized fully to carbon dioxide. Therefore, the energy used during moderate exercise is derived from a mixture of fatty acid and glucose oxidation.

Fuel usage (strenuous exercise)

As the intensity of the exercise increases even further (ie, running at the pace of middle-distance races), the rate at which the muscles can extract glucose from the blood becomes limited. In other words, the rate of glucose transport reaches Vmax, either because the blood cannot supply the glucose fast enough or the number of GLUT-4s becomes limited. ATP generation cannot be serviced completely by exogenous fuels, and ATP levels decrease. Not only does this stimulate phosphofructokinase, it also stimulates glycogen phosphorylase. This means that glycogen stored within the muscle cells is broken down to provide glucose. Therefore, the fuel mix during strenuous exercise is composed of contributions from blood-borne glucose and fatty acids and from endogenously stored glycogen.

Fuel usage in individuals who are unfit

Being fit (biochemically speaking) means that the individual has a well-developed cardiovascular system that can efficiently supply nutrients and oxygen to the muscles. Fit people have muscle cells that are well perfused with capillaries (ie, they have a good muscle blood supply). Their muscle cells also have a large number of mitochondria, and those mitochondria have a high activity of Krebs cycle enzymes, electron transport carriers, and oxidation enzymes.

Individuals who are unfit must endure the consequences of a poorer blood supply, fewer mitochondria, less electron transport units, a lower activity of the Krebs cycle, and poorer activity of beta-oxidation enzymes. To generate ATP in the mitochondria, a steady supply of fuel and oxygen and decent activity of the oxidizing enzymes and carriers are needed. If any of these components are lacking, the rate at which ATP can be produced by mitochondria is compromised. Under these circumstances, the production of ATP by aerobic means is not sufficient to provide the muscles with sufficient ATP to sustain contractions. The result is anaerobic ATP generation using glycolysis. Increasing the flux through glycolysis but not increasing the oxidative consumption of the resulting pyruvate increases the production of lactate.

Edited by jshann on 05/31/2008 19:54:48 MDT.

Fetch,
Your points number 5 and 6 just about say it all. You're absolutely right about one thing, though; further engagement would be pointless. As for upsetting my "apple cart of mammalian physiology, biochemistry......", all I can say is: You've got a great sense of humor.