This is, like said above, about the signals. After a while of starving, the body has to start to eat itself. It will eat fat, muscle, bone, inner organs, and (reaching my point) myelin. Myelin is a "fatty sheath" that cover our nerves, protecting our nerves like rubber protects an electric cable. The myelin makes it possible for the nerves to communicate with eachother, because electrical signals flow better through liquids/fat/water. When myelin is removed due to the body eating itself, this causes a worsened nerve communication. Which again often leads to falling, spraining ankles, crashing, etc. It can be harmful! Not only does it make traffic a dangerous place to be, it also puts the heart in danger. The heart requires adequate electrical signals in order to contract properly. Basically your heart can stop.
Avoid exercise. You body needs rest and energy to reverse this.