What the body goes through when it’s starving.
Starvation works in three stages. At each level certain activities are known to occur. At the first phase of starvation the body maintains the levels of blood glucose through the creation of glucose by breaking down glycogen, proteins and fats. Because of the fact that the body only has a supply of glycogen stored up to last a few hours it ends up turning to different supplies of energy. Fats and proteins are next on the list of possible energy sources. Everyone would love it if the body would just break down the fats in their system, specifically the excess fats that societies current standards tend to shun. And they do, to an extent. The body can and does break down fats into fatty acids and glycerol. This allows the rest of the body to use the fatty acids as energy and helps to save the glucose for the brain. However the body mainly forms glucose through the break down of proteins into amino acids.
Secondly the body starts to use fat as the “primary energy source” (Seeley, 2008, p. 947). This phase of starvation can last for weeks on end. Fatty acids get metabolized by the liver and are turned into ketone bodies. These ketone bodies are used as an energy substitute. If the lack of nutrients lasts long enough, the brain too will begin to use supplemental ketone bodies as energy allowing for a decrease in the need of glucose. Protein break down tends to diminish, but is by now means halted.
In the third phase of starvation the fat reserves have been depleted and proteins become the main source of energy. Here is when the muscles are targeted as energy sources. When push comes to shove the body ends up breaking down the proteins necessary for cellular actions, for energy instead. At this point it is only a matter of time before the person’s body ceases to function.
Seeley, R. R., Tate, P., & Stephens, T. D. (2008). Anatomy and physiology (8th ed.). New York: McGraw-Hill Higher Education.