Carbohydrates give you the energy you need to carry out your everyday activities and train hard in the gym.
When your carb stores are depleted too far, your body converts precious muscle-building protein into glucose for the energy it needs. Obviously, that's something you want to avoid. Therefore, you have to eat enough carbs to prevent it from happening.
Excess carbohydrates, however, get converted into fat. How can you avoid eating too many carbohydrates? One trick I've learned is to eat most of my carbohydrates in the morning and immediately after my workout'when my body processes them much more rapidly.