1. Glucose: Many cells in the body prefer glucose as an energy source. It's the body's main source of energy. After carbohydrates are ingested, it can be converted to glucose, which then circulates in the brain and through blood to all tissues. Carbohydrates, except fiber, can be converted to glucose.
2. Glycogen: The body's storage form of carbohydrates. It's made up of many glucose units linked together. The body can convert glucose to glycogen, which can be temporarily stored in the liver and skeletal muscle for ‘future use' when energy needs increase. The body can tap into glycogen stores if you've gone for extended periods with without food, if you have insufficient glucose readily available, or if your body requires more energy during activity. If glycogen stores become depleted, then the body can become fatigued.
3. Fat: If glycogen stores are at maximal capacity, then glycogen may be stored as body fat. Meaning that carbohydrates consumed in excess of what can be stored as glycogen can be converted to body fat. However, carbohydrates alone do not cause weight gain, excess carbohydrates, like any other macronutrient in excess can be stored as body fat.