It takes a certain amount of time to break down the first two macronutrients, therefore they are referred to as the "slow" form of energy, and carbohydrates that are broken down almost instantly are referred to as "fast."
Kuthatha isikhathi esithile ukuphihliza ama-macronutrients amabili okuqala, ngakho-ke babizwa ngokuthi ifomu lamandla "ahamba kancane," futhi ama-carbohydrate aphulwe cishe ngokushesha "ashesha."