Carbohydrates are used as energy by the body; they fuel our workouts, as well as providing ample fuel to be used throughout the course of the day. Ingesting carbs also replenishes our glucose and glycogen stores to prevent fatigue.
Carbohydrates eaten in excess, or eaten at the wrong times, can help to add adipose tissue to the body, but they are not a bad thing if incorporated into a diet properly. Eat the majority of your carbs early in the day and at the post-workout meal, tapering off on them as the day goes on.
Never eat carbs late at night, opt for protein instead. Sugar laden junk foods are always bad, and they are comprised mostly of carbs, and fat. In turn, they should have no place in a serious bodybuilders diet.
Use the following calculator to determine how many carbs you should be taking in each day. Remember to split these carbs up between each of your meals, and ingest most of the carbs early in the day and taper off in the evening.