Because the glycogen content in the body is relatively low during fasting exercise, the body's self-regulation system will make it more used to maintain normal physiology than exercise consumption. If you only do low-intensity exercise at this time, the body will mobilize more fat, including fat in adipose tissue, to supply energy, which will easily consume excess fat (especially postpartum fat), and the weight loss effect is better than after-meal exercise.
In addition, due to moderate exercise, the energy stored in the body is enough for the human body to deploy and use without affecting health.