During the workout session, your body goes through tremendous pressure and uses its nutrients to convert them into energy. If it is short of nutrients the chances of a person fainting are higher. Meal timings are to be taken care, consuming a large meal, needs time for digestion therefore, it is important to have it 2-3 hours prior to exercise. If the meal is more of a snack, try 1-2 hours prior. Consume high-carbohydrate, low-fat food. Fats are slow to digest, thus takes longer time to absorb.