The reasons are as follows: the human body still needs a fixed intake time of three meals a day. If you don't eat and exercise after 6 hours, running for too long will cause physical discomfort, hypoglycemia and even fever. Eating before running can provide enough energy for the body.
If you only want to lose weight, the fatigue after running can cover up your hunger, and the effect of losing weight may be obvious in the short term, but it is not recommended to lose weight at the expense of health, because the ultimate goal of losing weight is health.