The term nutritionist is widely used as it is not controlled like the title dietitian , but the word nutritionist can be used without having the qualifications of registered dietitians . A nutritionist is not a dietitian as he is not registered to a national board and does not have the same qualifications . The term `` nutritionist '' is also widely used ; however , the terms `` dietitian '' and `` nutritionist '' should not be considered interchangeable - the practice of nutritionist is not necessarily regulated .