The energy consumed by exercise is directly proportional to the intensity and time of exercise. The energy consumption in exercise mainly depends on the oxidation of sugar and fat, and the mobilization of fat metabolism in the body is slow, and more energy is supplied by fat for long-term exercise. Sugar is the main source of rapid energy supply for short-term exercise. Sugar exists in the body in three forms: muscle glycogen, liver glycogen and blood sugar, and its total amount is about 300 ~ 450g g. Total oxidation can only supply energy of 1, 200 kcal ~ 1, 800 kcal, and can only last for about 2 hours. If you exercise for a short time, don't consume much energy and have enough sugar reserves in your body, this situation will not do any harm. However, if the sugar reserves in the body are insufficient, fasting exercise will consume or even exhaust the sugar reserves in the body, which will lead to hypoglycemia, dizziness, black eyes, pale face, leg weakness, sweating, inattention, disorientation, convulsions and coma.
Generally speaking, before high-intensity exercise, it is not appropriate to have an empty stomach, and some sugar foods should be supplemented appropriately; For general fitness exercise, it is possible to have an empty stomach as long as it is not too long and strenuous exercise. Of course, the premise is based on the situation before the exercise. If the sugar reserve before exercise is insufficient, it is necessary to supplement sugar or appropriately reduce the intensity and load of exercise. If hypoglycemia really occurs during fitness exercise, you should immediately stop exercising, rest in place and observe your body reaction. It is best to drink some sugary drinks to relieve the symptoms of hypoglycemia.