In the previous article we covered the basic myths of food and what not to do. Our tips are:

• Don’t carry too much - leave the tins and puddings home. Carrying excess is guaranteed to ruin your walk
• Don’t follow fads or try to diet on trips - this is not the time to try new things.
• You don’t need to buy “specialist” hiking food - everything you need can be found in the supermarket.
• Eat what you are familiar with.

In this article we cover what types of foods are suitable and the quantities required on a walk.

What is food?
Food is fuel for the body. If we don’t fuel the body we stop. Like a steam train we shovel stuff in one end, we burn the fuel and we get locomotion. Stop shoving stuff in and we soon grind to a halt. If we have a big engine and we want to go fast up hill with a heavy load then we need more fuel. Like the steam train the body has its own “combustion” process called the digestive system. This converts fuel to energy-laden blood cells, which are pumped by the heart through the arteries to the muscles, which convert the energy into locomotion. The train uses steam to provide the energy to operate pistons, which drive the wheels.
Carbohydrates and fats in our food supply energy.Energy can be measured, and the measurement unit is the kilojoule.
Food also provides the raw material to repair the body through tissue replacement. Proteins found in meats, eggs, fish, milk and cheese provide some energy and the material for tissue replacement.

Mr Joule, his wife Calorie and their dog kilo.
An amazing discovery by 19th century scientists means we can use a single quantity to directly equate the energy of food, lumps of coal, petrol, keeping the light on for 1 hour, walking home with the shopping and flying an airplane from Melbourne to Sydney. Energy like money is a universal means of exchange. Everything within our economic system has a price, and we can exchange almost anything by converting its value to money first. Everything within the physical world has an energy value and we can use this value to determine what we get when we convert one thing to another.
James Joule was the 19th century English physicist who discovered that heat is a form of energy and whose name graces the unit of energy measurement.
No he didn’t have a dog called kilo - (kilo means 1000) and he wasn’t married to Calorie. Calorie is the imperial unit of energy measurement and no longer is use in this country.
Energy values allow us to determine how far we can walk on one ham sandwich. If we want to go on holiday to Europe we need to budget around $150 per day. If we want to go on a bushwalk we know we need to budget around 15,000 kilojoules per day, for a large male on a strenuous walk. For a recreational walker the allowance is likely to be closer to 10,000 kilojoules. All we need to do is convert any type of food to kilojoules to work out whether we have taken enough. This information is available from books called kilojoule counters, which will provide you with details of the energy, protein and fat content of all types of food.

How much is enough?
A balanced diet should consist primarily of carbohydrates, with fat and protein in lesser quantities. The recommended balance is 5-7g of carbohydrate and 1 g protein per kg of body weight. Fat should be kept to a minimum to allow for the high carbohydrate needs, and would be around 2g /per kg of body weight depending on an individual’s energy requirements. Bread, cereals, pasta, noodles, sweets, biscuits, dried fruit and potatoes are carbohydrate rich and are the preferred source of energy for walks. When using these guidelines and after studying the kilojoule counter you will find that about 900g - 1000 g of dry weight food per day will be required to satisfy the average energy needs.
By dry food, we mean food that has the water removed, such as dry pasta, cereals, breakfast bars dried fruit and dried vegetables. Fresh fruit and vegetables consist of about 80% water, so if you are carrying these then the weight requirements increase significantly. For this reason the use of fresh fruit and vegetables is limited to walks less than 3 days.
This rule 900-1000g per day has been used by bushwalkers for many years and, from experience, it does work. Individuals have their own preferences and may require as little as 600g per day for smaller people on medium walks up to 1300 g per day for larger individuals on strenuous walks. I have taken 7kg food on a 10 day walk (700g per day) and have eaten quite well without going hungry.

Fats and carbohydrates - What is the best?
When studying the kilojoule counter, you may have noticed that high fat foods have almost twice the energy value per gram compared to carbohydrate foods. Ah ha! you say. I can eat fatty foods and save half the weight on a long walk. I’m fit, I can eat anything - no problem, Macca’s here I come. Wait, not so fast!!.
The problem is that when the body is exercising, it prefers to use carbohydrates before fats. Although fats have more energy per gram, they need more oxygen per gram to convert into the same amount of energy. During exercise the body will mostly consume carbohydrates because the amount of oxygen available is not sufficient to use fats to meet the energy requirements. The body can utilise fats, but it cannot use fats and maintain the same energy compared with carbohydrates. When the body is only consuming fats it will slow down to match energy output to the available oxygen. This is called “hitting the wall”. Its like putting the handbrake on in the car or wearing lead boots. That’s why we need to consume mainly carbohydrates.
Our bodies carry limited quantities of carbohydrate but almost unlimited quantities of fats and proteins, The fit person has about 600-700g of carbohydrate stored which will last for 60-90 minutes of intense exercise. Fat stores are a massive 5-10 kg, which will last for 15,000 minutes of brisk exercise. Our fat stores are like having money in the bank. Carbohydrates are like cash in the wallet - they are convenient and easily disappear, but are only available in limited quantities and need constant replenishment.

The importance of being fit.
The other important factor is the individual’s level of fitness. Fit people have trained their bodies to consume fewer carbohydrates and more fats for the same energy output. Back to our example with the spending money on our European holiday. We have $10,000 in the bank (our fat stores) but our wallets can only carry a maximum of $100 in cash (carbohydrate stores) and we need to spend $150 per day. Fit people are like experienced travelers who learn to use cheques or credit cards to make direct (non cash) withdrawals from their bank (fat stores) and extend their use of available cash for more than one day. Unfit people are like travelers who only spend cash from their wallets. They don’t have enough cash to last the day and will either have to stop spending (reduce their activity) or go to the bank twice a day (rest and eat more food). Once the body has used up its stores of carbohydrate (money in the wallet) it will be forced onto using fats (going to the bank).
That’s why it is very important to be fit before undertaking medium or hard walks. Unfit people can often start reasonably well in the morning but flake out early on the trip or when the going gets tough climbing a hill. Their wallet has run out of money and they “Hit the Wall”. Even fit people need to manage their energy levels with frequent rest stops and proper lunch breaks to make it through the day. In fact a well-managed, less experienced group of bushwalkers can often beat an impetuous and gung-ho group given the right leadership.

In summary we /would recommend:

1. Carry around 900-1000g in dry weight food per day
2. Ensure you eat mainly carbohydrate - 5-7g per kg of body weight per day
3. Ensure you are fit for medium and hard walks
4. Eat well and take plenty of breaks on walks to manage your energy levels.