The first few days without food are a critical time for anyone trying to make the step from survivng to living in the wilderness. It is in this period that we exhaust the body's store of carbohydrate.Because carbohydrates such as starches and sugars are composed of simple, easily digested molecules, they are an efficient food source that can be digested with little waste. Quickly and easily converted to energy, carbohydrates are vital in the supply of energy to the brain and nervouse system and are consequently utilised before the other food sources of fat and protein.
We store carbohydrate in the muscles, the liver and a small amount in the blood. For use this is converted into glucose then transported to wherever it is needed, particularly the brain and nervouse system , by the blood. The rate at which we exhaust our store of carbohydrate depends on how hard we are working, but can be as little as 3 or 4 hours when working hard in a cold environment. When our reserve of carbohydrate is exhausted our blood sugar level drops resulting in a reduced supply of energy to the brain. Because the brain is unable to store energy for ityself it demands a continuous supply; when there is a reduction in supply various symptoms are triggered: tiredness; headache; easy irritation; loss of concentration; reduced ability to make decisions; depression; increased susceptibility to cold; increased concern with oneself.
As time goes on, fast intensive work becomes difficult; even walking up a moderate slope seems impossible. Tasks which at other times would be straight forward, such as crossing water, now become hazzordous.
An excert from Essential Bushcraft by Ray Mears.
