Original: 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.
Simplified: 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.