It is true because if you train to hard you are gonna get overload syndrome.
Fibers and Starches are complex carbohydrates or complex chains of sugars that are used to store energy in plants. Plants also create some simple sugars that they will use for primary energy like Sucrose and Fructose.
Us humans use Glycogen as a complex carbohydrate to store energy in case of starvation, and we use glucose as a simple carbohydrate.
