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Notes On Rations, Supplements & Energy Metabolism

Notes On Rations, Supplements & Energy Metabolism

Food: A Work In Progress

Last Updated: 20/05/20

Please note that Part 2 is very much a work in progress and likely to change. However, the basic principles are there and when we're happy with an initial draft, we're going to post it. 


This post is going to be updated fairly regularly but we wanted to get the bare bones version out. When we update it, we'll "republish" (i.e. the published date will change, rather than the updated date) so it will re-appear from time to time as the latest post.

Obviously food is largely about taste preferences; there's no point carrying stuff you can't stomach, but this post is not so much about the subjective; instead it's about the how to fuse personal tastes with the objective (energy density, nutritional value, weight etc...) and the pragmatic (packability, shelf-life, cook-time etc...).

There's no Scramble consensus around the ideal menu for long distance treks, and so since the editor (me) has a more geeky interest in the science around energy metabolism and nutrition, I'll go out on a limb and just tell you what I do and why I do it. In the process I'll aim to provide a reasonably concise outline of some of the latest research on the fuels we consume, store and burn.

Since body composition and gender is of some contextual relevance (and perhaps biological age, but that means we have to get into Horvath's epigenetic aging clocks and DNA methylation, which we're not doing here ... so), let's see who's doing all the talking:

Scramble Editor - Vital Statistics



Part 1: The Practical
Part 2: The Theory (Work In Progress)

Part 1: The Practical

Capacity: Food in terms of Cubic Litres

Before we get into exactly what's being consumed, let's see what size "tank" we need to store all this fuel. Below are pictures from the 2019 Summer Kit Test; I was carrying 10 days worth of food. In picture #1 (left image) the remaining 9 days of food is filling approximately 17 - 18 litres of space (the pack is a 70g Sea To Summit 20L Ultra-Sil Day Pack). This doesn't include drinks (teas) or supplements, which I carry separately with each day's food rations (pictured below, #2 right). 

For the 2019 Summer Kit Test, I was using the excellent Blue Ice Warthog 40L pack. Setting out, about half the pack's capacity was taken up with food. When budgeting for capacity, I think a reasonable approximation (at least in my experience with the types of foods I'm consuming) is between 2L and 2.25L per day (for just the food).

9 Days of Food (#1) and 1 day's rations with 10 days of teas and supplements (#2)9 days of food supplies in a Sea To Summit 20L pack (left) and 1 day's rations with 10 days worth of tea and supplements (right.)

Teas, supplements and the day's food supplies are packed (outside the main body of the pack) with my cooking kit in a Cook Kit Stuff Sack (25g) and this all fits easily (along wth plenty of other stuff) inside a Scramble 11L Tower. Here's the full list of contents as pictured below (#2 right):

Daily rations are stored with the cooking kit outside the main body of the pack (for easy access)Cooking kit, 1 days rations and 10 days teas and supplements.

Weight: Food in terms of Energy (Calories) per Gram

During a trek, I'll burn approximately 6,000 kcals per day, yet only carry between 2000 and 2500 kcals of food. That 3500 to 4000 calorie deficit, after a few days (more on this later) begins to use up body fat stores.

For the 2019 Summer Kit Test, my daily rations contained 2381 kcals (which is a little higher than normal) and this weighed in at 644g (at a calorie density of 3.70 kcal / gram). 644g / day = 6.4kg for the 10 day trek (Summer Kit Tests are normally a bit longer, but we had a lot going on).

The point here is simply this: food is heavy. The main reason we're carrying it is to provide some buffering against the inevitable drain of body fat stores. We want as much calorific bang for our buck (while not entirely sacrificing nutritional value) and this means energy dense foods. Which is why the most important number on the spreadsheet pictured below is calorie density. I try to keep this number between 3.5 and 3.8 kcals per gram.

Calorie Density is the Key Metric

We'll get into the types of food later. But anyone with a keen eye may notice a calorie dense food not on the list above: cheese. This is not a strategic omission;, it's merely one of those pesky taste preferences. I simply can't stand the stuff (though I really wish I could).

Time & Taste: Food in terms of the "What" and the "When"

Before we get to the differences between summer and winter eating, for me at least, some things remain consistent across the seasons:

  1. flapjacks are my go to energy booster
  2. custom fruit and nut mix (70g) for breakfast
  3. favourite meal

When it comes to dried starchy carbohydrates (fillers like rice, noodles, pasta etc.) I stay clear of anything that requires a long boil time to re-hydrate / cook. Couscous and noodles are ideal as you just add boiled water and let them sit, so your gas usage is kept to an initial boil (you don't need to keep the water on the boil, as you would with rice for example). 



I find flapjacks the ideal energy and morale booster. For long duration (>10 days) treks I'll carefully plan where I can re-supply. Pictured below is a fresh (mid-trek) consignment (from 2017 I think).

A 1.2kg boost to morale & energy levels

Fruit & Nut Mix

In terms of nuts, you ideally want the high fat / low carb nuts (but you need to balance this with ease of digestion). For example, walnuts are high in fat, but as much as I enjoy them normally, I find them hard to consume when my body is under continual physical stress (they seem dry and dusty and hard to get down). Cashews are higher in carbohydrates (and lower in calories) but much easier to consume. I tend to mix cashews with high fat variants like pecans, macadamia and brazil nuts. I include a few sultanas in the mix as they're sweet, juicy, easy to eat and contain fibre (pumpkin seeds are a nice tasty option too to increase fibre content).

Favourite "Recipe"

Please keep in mind this is purely subjective, but here goes:

Chicken Pasta, Chorizo, Olive Oil and Cream Cracker 'Croutons'

  • Empty 1 x Mugshot ("roast chicken pasta" is best) into a bowl
  • Add in your carefully sliced Chorizo (1/4 to 1/3 of a 227g ring)
  • Add (extra virgin) olive oil (I take 50ml so that leaves about 5ml per meal)
  • Then add boiling water, stir and leave to sit for 5 minutes
  • Add cream crackers (4 or 5 broken up), mix in and consume while they're still crunchy

The Mugshot and the cream crackers have practically zero nutritional value but they do provide energy. The nutrition is in the protein and the fat (Chorizo and olive oil).

Seasonal Variations on a Theme

Summer: Longer Days, Better Conditions

In summer when the days are longer and the weather is more conducive to a short "lunch-break", I tend to go with a 3-meal-a-day regimen. I'll have a 70g portion of fruit and nuts for breakfast (pictured below, #1).  "Lunch" and "dinner" (#s 2 + 3 below) are interchangeable, though in my view the biggest meal is best had in the middle of the day and the lighter meal is best left for the evening.

A Typical Summer Day's RationsSometimes noodles, sometimes couscous, sometimes fish, sometimes sausage.

If you take vitamin C, this should also be consumed at the end of each day (rather than the beginning). We'll see why in the "teas and supplements" section.  Whenever I need a boost throughout the day, I'll dip into my flapjack supply (#4 above).

Winter: Shorter Days, Worse Conditions

In winter, things are quite different. The number of (static) meals drops from three to two (sometimes one). I try and start each day the same as I would in summer, with nuts (but sometimes I need something more sugary and may supplement or replace the nuts with a flapjack to get going). Sometimes, I'll skip food entirely and just have a cup of tea.

The main meal (#2 and 3 above) is reserved for the evening. I'll make big reductions in the number of Kimchi noodles I take and switch them out for the equivalent weight in cold (eat-on-the-go) sausage (generally Podwawelska, smoked polish sausage) as some meats (like Chorizo) are a little chewy and work better in hot dishes.

So, in winter I'm much more flexible about when I eat (except for the meal at the end of the day). If I don't feel like nuts in the morning, I'll eat them on the go. I'll eat cold meats on the go and flapjacks too. Since days are shorter, I'll be trekking for at least 2 hours a day less in winter. I also rely more on burning body fat and so in total I'll carry less food overall in winter than I will in summer.

This may seem somewhat paradoxical, but winter gear is heavier and so carrying less calories means less pack weight. I'll put on weight pre-trek and for at least one week I go on a strict OMAD (one meal a day) "diet" - this means you stuff your face and then don't eat a single item of food for the next 23 hours. This gets the body more attuned to fat burning, so body fat stores are more accessible during the trek (much more on this in Part 2).

Teas & Supplements

Foods that are easy to pack, have a long shelf-life and are high in calories aren't necessarily very healthy or nutritious. I daren't contemplate my current state of health (if alive at all) if my regular diet consisted solely of my backpack rations.

In regular life, I try to maximise healthy fat and protein intake and include a reasonable amount of green leafy and cruciferous vegetables. I keep to a minimum what is referred to as "empty carbs"; the starchy often highly glycemic vegetables and grains, like bread, potatoes, rice, pasta, noodles etc..

This kind of diet is almost impossible to carry over into the trekking domain. Healthy food tends to rot. Supplements are an imperfect and lightweight way to, if not remedy, at least ameliorate the inevitable malnutrition of a long duration trek.

Oolong & Ginger Teas + SupplementsOolong & Ginger Teas, Cod Liver, Vitamin C, Magnesium, K2 & B Complex.


Here I'll just outline what supplements I take and why I take them (where necessary I'll briefly state what physical processes they're involved in).

Vitamin B-Complex [thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9) and cobalamin (B12)] are water-soluble vitamins required as coenzymes for essential cellular and metabolic functions. The main reason I take them is they are required inputs for (the krebs cycle) energy metabolism and though B12 for example is recycled, my view is that if my body has enough (of each of these), they will be excreted. None of the foods I pack with me are particularly good sources of B vitamins (except fish when I carry it).

Vitamin C is a powerful anti-oxidant which helps counter oxidative stress; elevated intracellular levels of reactive oxygen species (ROS, generated by continuous physical exertion) that damage lipids, proteins and DNA. However, ROS act as powerful signalling molecules for skeletal muscle adaptation during periods of prolonged, strenuous physical activity. For this reason vitamin C is better taken after, rather than before, intense physical activity.  I take 2000 mg each night (of the fizzy tablet orange drink kind).

Cod Liver Oil contains large amounts of omega-3 fatty acids (as well as some vitamin A and D). Omega 3’s are components of cell membranes, essential for hormone production, beneficial for cognition and are used by the immune system to suppress key inflammatory genes and thus dampen inflammation. They also help to counter the inflammatory omega 6's found in nuts.  

Vitamin D3, K2 and Magnesium

Vitamin D (taken in winter only) is not a vitamin, it's a hormone synthesised in the skin upon exposure to sunlight, then metabolised in the liver and kidneys into D3 (it can be taken via supplement in its active form D3, and in minuscule quantities from some foods like oily fish). Vitamin D regulates the expression of anywhere between 5 and 10% of the human genome, it's essential for both cellular metabolism and immunity; controlling calcium homeostasis and modulating the response of the innate and adaptive immune system.

Magnesium activates more than 600 enzymes and influences extracellular calcium levels. Skeletal muscles, heart, teeth, bones, and many other organs require magnesium to sustain their physiologic functions. Magnesium is essential for the stability of cell function, RNA and DNA synthesis, and cell repair, as well as maintaining the antioxidant status of the cell. All of the enzymes that metabolise vitamin D seem to require magnesium, which acts as a co-factor in the enzymatic reactions in the liver and kidneys. Deficiency in either of these nutrients is reported to be associated with various disorders, such as skeletal deformities, cardiovascular diseases, and metabolic syndrome (source). Even though I get a little in my small portions of nuts and fatty fish, it's so essential that I'd rather have too much than not enough.

Vitamin K2 (menaquinone) is found in animal and fermented foods. There are two important sub-types: MK-4 and MK-7 (I take MK-4 one day,  MK-7 the next). Vitamin K2 activates proteins that play a role in blood clotting, calcium metabolism and heart health. Vitamin K2 works in conjunction with vitamin D3 (from sunlight or supplements in winter) to  ensure that calcium reaches the bone while inhibiting arterial calcification and arterial stiffening.


Aside from taste there are some objective reasons for choosing the two teas I take with me all year round. In the film Angel Heart, Charlotte Rampling's character states "not many people like oolong". It may not be to everyone's taste but I love it; extremely refreshing in summer and winter with some healthy side benefits. The other tea I carry is ginger; warming in winter, but still a nice change on a cool summer night.

Oolong tea is slightly fermented and partially oxidised and sits between a black and a green tea. High in caffeine, Oolong tea elevates metabolic rate and increases fat oxidation. The tea's polyphenols are associated with reductions in visceral fat and have anti-oxidant and anti-inflammatory properties. 

Pure ginger tea contains gingerol, shogaol, and other substances which, like Oolong have both anti-oxidant and anti-inflammatory properties. Ginger aids digestion and helps settle the stomach, which is useful when eating a non-optimal diet. It has anti-bacterial, anti-fungal and anti-viral properties and may be effective against respiratory tract infections, fungal infections and likely gum disease. A study published in Arthritis and Rheumatism showed that ginger extract was able to significantly reduce knee pain caused by osteoarthritis, probably through its anti-inflammatory effects.


Part 2: The Theoretical

In this section we'll look into some of the theory and recent research related to how our bodies actually work: glucose versus fat oxidation, metabolism, mitochondria, blood sugar and a couple of important hormones: insulin and glucagon.

Energy Metabolism: A Brief Evolutionary History

Or "Why do we have a gaping hole in our face and two bags in our chest?"

A few billion years ago life was pretty simple on planet earth. Populated by mono-cellular life-forms (think yeast) which were immortal in the sense that they had enough energy to make single copies of themselves (via cell-division and had no mechanism for self-annihilation) but didn't have sufficient surplus energy to do much else. These mono-cellular life-forms thrived in a hypoxic (low oxygen) environment and made energy by fermenting sugars.

A bacteria called mitochondria was cohabiting the planet and (for some reason I am not aware of) an almost faustian bargain seems to have been struck (around a billion or so years ago) between these bacteria and their single-celled friends. The bargain laid before the uni-cell beings was something like this:

You can remain immortal but you will never grow into anything but another copy of yourself OR you can fuse with these bacteria called mitochondria; this will give you a major energy boost (about 19 fold) and this energy surplus will allow you to become complex multi-cellular lifeforms BUT you will also become mortal and the mitochondria will have the keys to your mortality (the mortality of each cell). Individual cells when old or dysfunctional will be "suicided" via apoptosis (regulated cell death) for the good of the collective; the multi-cellular entity.

Sign on the dotted line (said Mephostophilis) and with a few skips, hops and a jump, here we are today:

A combination of cells whose energy largely derives from hundreds of tiny bacteria in each cell (about 700 organelles on average) which via something called the electron transport chain act as micro power stations catalysing fat (fatty acids) or carbohydrates (glucose) and oxygen in a process called Oxidative Phosphorylation (OxPhos) to form intra-cellular energy, ATP (Adenosine Triphosphate). This is cellular respiration and when this process stops due to a lack of oxygen or fuel, we die ("suffocate" or "starve").  

So that's why we have a gaping hole in our face and two bags in our chest - to fuel our bacterial power stations. A mouth to consume fuels (fats and carbohydrates) and breathe in air (oxygen) for our lungs to process for transportation via the hemoglobin in our blood cells (which are themselves free of mitochondria - since you don't want the waiter picking at the meal). The fuels and oxygen take different routes into our blood for delivery to the mitochondria who tranform them into ATP (energy) + Carbon Dioxide (waste product) which we exhale (don't tell Greta!). This whole process is called the Krebs (or tricarboxylic acid) cycle; a process more easily understood as energy metabolism.  

I'm trying to keep things as simple as possible here. The process actually looks something like this:

Image courtesy of Journal of Endocrinology, 220

Pathways of substrate metabolism in muscle.
Source: Journal of Endocrinology 220, 2; 10.1530/JOE-13-0397

The Human Cell

Just a quick word on the structure of a cell. The cell has three main parts: the membrane (the outer wall) the nucleus (which contains the DNA, the copy manual) and the stuff in between called the cytoplasm - this is where the mitochondria operate. Interestingly the kill switch is controlled by the mitochondria (they regulate apoptosis) but the replication instructions are contained in the nucleus. This is an interesting and extremely important division of function (and gives us a clue as to the nature of cancer whose defining feature is immortal and unregulated cell growth - i.e. the faustian contract referenced above got ripped up).

Fuels: Fatty Acids (Fat), Glucose (Carbohydrates) & Ketone Bodies

Fatty Acids & Glucose

Evolution can give us a guide as to which is the better fuel to burn (it's a complicated topic) and if you want a deep dive into this I'd strongly recommend the following conversation between Peter Attia (MD) and Iñigo San Millán (Ph.D):
"Mitochondria, exercise, and metabolic health"

But when considering the three macro-nutrients: carbohydrates, fats and protein, one has to wonder why one of them we can survive without. If you don't consume any fat or any protein you will die. That is not the case if you consume no carbohydrates. One of the reasons for this is a process called gluconeogenesis:  gluco (sugar) neo (new) genesis (creation). The body is able to convert non-carbohydrate carbon substrates like amino acids (protein) into glucose (sugar) via the liver. The body is able to satisfy essential glucose requirements endogenously, without necessarily relying on exogenous carbohydrate intake.

Also noteworthy (and something of a clue) is that carbohydrates, broken down as glucose can be converted to fat (a process called de novo lipogenesis) but fat cannot be converted into glucose. As far as I'm aware the only cells that rely solely on glucose for energy are astrocytes (glial cells in the brain). Though, if you read the UK government's dietary guidelines you would assume the contrary; that carbohydrates were the essential macronutrient and that glucose was the key to our metabolic health (but then again they've presided, in bipartisan manner, over an explosion in metabolic disorders and pathologies from type 2 diabetes and obesity to cancer and neurodegeneration, so hey).

The UK Government's Healthy Eating PlanThe UK Government's Eatwell Guide (right click > view image, for a larger version)

All three macronutrients, carbohydrates (glucose), proteins and fats (fatty acids) can be broken down and oxidised to provide energy. However, protein is not really a "native" fuel; it must first be converted into glucose (as described above) by the liver. Both glucose (in the form of glycogen) and fat (lipid droplets called triglycerides) are stored in various tissues. Muscle tissue is a major storage sink for both fatty acids and glycogen stores and the liver maintains an essential reserve of glycogen to maintain blood sugar levels.

To survive, at least in the old days, we used to have to be able to think and move. That means energy demands from the brain, skeletal muscles, heart (and essential organs) have to be met. Like any well designed system, the human body is replete with backups and built in redundancies.

Ketone Bodies

When it comes to making energy the body can oxidise fatty acids (FA) or glucose. When FAs are oxidised (during periods of fasting, carbohydrate restriction, starvation, prolonged intense exercise) the liver produces ketone bodies. Producing ketones, referred to as being in ketosis, is symptomatic of the switch from glucose to fat metabolism.

Ketones are water-soluble molecules (acetoacetate, beta-hydroxybutyrate) produced in the liver, converted into acetyl-CoA, where they enter the Krebs cycle (pictured above) to be oxidised in the mitochondria for energy (ATP).

A dogma that still persists today (even in the medical community) is that the brain solely relies on glucose for fuel (and thus the importance of carbs, gluconeogenesis and glycogen stores in the liver), but this isn't true. In fact, in the presence of both glucose and ketones the brain will preferentially metabolise ketone bodies. 

As well as being an alternative and preferential fuel source for the brain, ketones are important signalling molecules that trigger a range of epigenetic processes involved in the reduction of inflammation and oxidative stress (ROS), the up-regulation of both mitochondrial respiration and the endogenous anti-oxidant system as well as improved memory encoding in the brain via the inhibition of histone deacetylases (HDACs).

So that's our fuels: fatty acids (FA), glucose and ketones. We'll put ketones aside for the moment as we check our fuel tanks for available glucose, glycogen stores and triglycerides (FA) stored in adipose tissue (fat cells) to see how much energy we can actually store in our bodies.

... coming soon.


Last Updated: 20/05/20

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