Must be valid. I lost weight like this 13kg. Up to now, several months have passed without any rebound. People around me have lost weight when they see that I am effective. Now each of them has succeeded, and there is no rebound. There are bound to be side effects, especially in the first stage. The first day is fine, and the next day will be a little uncomfortable. This depends on the actual situation of the individual. On the third day, I vomited once. It was all sour water, but it was not serious. My roommate had a cramp in his foot the next night, and then took calcium tablets. The other roommate has no side effects at all and goes running every day. In fact, after these three days, the back will be fine. It is suggested to drink some honey water and buy some calcium tablets for later use during the hunger strike. As long as this method is used, it will be successful. Come on!