What is the minimum amount of food
that I need on a walk?

Many enthusiastic walkers have often asked me this question, which I will attempt to answer based on an analysis of metabolic requirements. This article will not present menus or recipe ideas, but rather nutritional indices which you will then need to apply to your own requirements and tastes. It will require you to look at the composition of foods that you might like to carry, and adjust quantities accordingly.

I must emphasize that these are basic metabolic requirements to provide you with fuel for a walk of 2-3 days. They will not provide you with a nutritionally balanced diet or adequate roughage for an extended walk of a few weeks. They also do not account for any particular medical dietary requirements.

The main components of our diet can be classified biochemically as proteins, carbohydrates, or fats. Another important component is the part that is usually not digested and which adds to the bulk of our faeces ie roughage.

I will refer to the quantities required for the average person as grams per kilogram of body weight per day.

Carbohydrate is the best source of energy for a walk. The amount of carbohydrate required as fuel will depend on the exertion of the hike. The amount will range from 5 gram/kg/day for a light walk up to 30 gm/kg/day for a strenuous climb. While we can store a limited amount of carbohydrate from the night before, it is best to provide this fuel continually during the exertion. Any excess intake of carbohydrate will be converted into fat. A snack every 4 hours would be ideal. An oatmeal breakfast and a damper for during the day would meet this requirement.

Protein can be used for repair of tissues and as a source of energy. The energy derived from protein is roughly the same as that derived from carbohydrate. However, metabolism of protein as an energy source creates a greater need to excrete nitrogenous compounds in the form of urea, which then requires more water. The minimum protein requirement for repair of tissues is 1gram/kg body weight/day. A small tin of tuna or two eggs would provide enough daily protein for an adult. The protein is best consumed at night, when it will be available for tissue repair and not burned for energy.

Fat provides twice the amount of energy provided by protein or carbohydrate, but is also the most difficult to burn as energy. High fat snack foods are usually just deposited as excess body fat. Unless you are especially lean, it is probably easier to simply burn your own body fat, rather than carry fat in your pack that once eaten simply gets transferred onto your body weight.

Adequate roughage enables us to form and pass bowel motions comfortably. This can make a considerable difference to our comfort on a through walk. The best roughage comes from leafy green vegetables or from fibre in whole grain cereals. Such vegetables are more valuable than fruit on a walk.

If you want to travel really light, then a daily multi-vitamin supplement and a fibre supplement powder can be obtained from the pharmacist.

Beverages such as tea or coffee should be consumed only when additional fresh water is available as they have a diuretic effect and will actually deplete the body of water an hour or two later. Similarly, concentrated soup powders have a high salt content and will cause extra body water to be excreted.

If salt depletion is a concern in hot climates, it can best be replaced by the use of a dilute re-hydration fluid such as "Gastrolyte" or "Glucolyte" available from the pharmacist. The powder can be added at half the recommended strength to the drinking water. Do not use concentrated "Sports" type drinks that may actually steal water from the bowel.

Remember that these are suggested minimum requirements only. Individuals will need to determine their own energy requirements. The difficult part is to convert these principles into a palatable diet.
Venite ac capite!
Frank Bowling

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