Some people think that running on an empty stomach will lead to insufficient blood sugar supply, causing physical weakness and even impaired liver function. In fact, there are three ways to supply energy during exercise, and long-term running mainly depends on glycolysis and aerobic oxidation (in fact, glycolysis also belongs to aerobic oxidation, which means being directly decomposed by glycogen in the body; Aerobic oxidation here emphasizes the decomposition of fat to provide energy).
Besides extreme load or explosive training, aerobic oxidation is the main way to provide energy for exercise. After 2 minutes of exercise, glycolysis becomes the main way of energy supply. Of course, fat also began to participate in the process of energy supply and gradually occupied a large proportion. When you continue to exercise for 30 minutes, the proportion of fat energy supply reaches its peak.
Therefore, for running for more than 2 minutes (actually, it can be understood as long-distance running above 1 km), the energy supply does not depend entirely on liver sugar. Because of biological evolution, we humans have always been accustomed to storing fat as a "war preparation material". Normal people have fat support, so there is no need to be afraid of running on an empty stomach. The hypoglycemia mentioned above is caused by dietary problems in some cases. At this time, it is enough to supplement monosaccharides (glucose, honey); If it is caused by hepatopancreatic dysfunction, it is necessary to see a doctor.
Of course, if it is a competitive long-distance race, people will replenish drinks-mainly sugar, salt and vitamins-half an hour in advance, but generally they will not eat more solid things.