To help understand our body's energy requirements let us compare it to the motor car. We all know that if you don't put fuel in your car it will not go. The same could be said of the human body if we do not fuel the system it will not function properly and will eventually be unable to move.

If you put the wrong fuel in your car, the cars best performance will not be achieved. Once again the same can be said of the human body, if the wrong fuels are used it may function, but only for a short period of time, or it will be lethargic and not want to do anything.

If you drive your car really fast it requires more fuel over a shoter distance. Once again the human body also requires more fuel, when you work it harder or require more from it. It is not just physical activity that necessitates this requirement for more fuel. Mental activity or thought stimulation also makes the brain use more fuel.

However there is one major difference between the human body and the car. If you were to put diesel in a petrol car, not only would it not run; it could also ruin the engine. If however you put the wrong fuel in the human body it has the ability to manipulate the fuel source by various processes within its engine to be able to use that fuel. Now it may not be the most effective fuel for the job, but the body will be able to derive some energy from it.

The fuel utilisation and anaerobic/aerobic sections will help you to understand the fuels we require and how they are processed.