You can't. A nutritionist refers to a person who can guide people in diet through strict basic nutrition theory study and professional clinical nutrition skills training. Without a nutritionist's certificate, he knows that others lose weight because he has no training and can't formulate training suitable for others, which will further damage others' health, so he can't guide others to lose weight. Nutritionist certificate refers to the public dietitian qualification certificate, which means that students who pass the appraisal examination will get the national vocational qualification certificate of public dietitian uniformly printed by the Ministry of Labor and Social Security, recognized by the state and used nationwide.