It is not advisable to do a valley break during menstruation, as a weight loss method, it is easy to consume a lot of fat and muscle, which is a blow to the qi and blood, and the requirements for qi and blood are very high during menstruation. If the menstrual period is open, not only can cause the human endocrine system disorders, but also cause the appearance of some diseases, such as delayed menstruation and other menstrual diseases. It is recommended that the time to start a valley should be after menstruation to avoid further damage to the body and to make the valley more effective. The estrogen of the human body fluctuates greatly after menstruation, and this phase is very conducive to the Purgatory to consume fat, rather than consume a lot of muscle.