Foods high in simple sugars, like soda or candy, lack substance to sustain blood sugar which may result in an energy crash. Simple sugars tend to give a short-lived energy spike that may not last as long as you need it. Choosing complex carbohydrates prevents blood-sugar crashes due to the amount of fiber. Fiber is considered an energy stabilizer because it allows the body to receive a steady stream, rather than a tide, of energy into your bloodstream. You can become "more complex" by adding in foods such as whole wheat bread, brown rice, couscous, bulgur wheat, high fiber breakfast cereals, beans, whole fruits, and vegetables. A major superstar food for energy is oatmeal because it is low on glycemic index, loaded with fiber, and contains stress-lowering B vitamins which help turn carbohydrates into useable energy.