How to Differentiate Good Carbs from Bad Carbs Good carbohydrates are generally high in fiber and nutrients and low in fat. Fiber lowers the glycemic index of foods by releasing glucose into the bloodstream. Bad carbs have a high glycemic index. They quickly increase the level of glucose in the blood and provide a low supply of nutrients and fiber. Carbohydrate and electrolyte supplements help to maximize your endurance, optimize recovery and increase your power.sance.