First, it is not advisable to run on an empty stomach or after a full meal. If you run for a long distance, you can drink a small glass of sugar water or eat less snacks first.
Fasting exercise leads to a significant increase in free fatty acids in human blood. If there are too many free fatty acids, there will be "poisons" that damage the myocardium. This "poison" often leads to abnormal heart rhythm and even sudden death.
Second, running after meals or eating immediately after running will reduce gastric acid secretion and affect food digestion. Over time, it will cause stomach problems. Generally, it is better to exercise after meals 1 hour. Running before going to bed is not good, and exercise before going to bed makes the cerebral cortex in a state of high excitement, resulting in adverse reactions such as dreaminess or difficulty in falling asleep.