The titles Registered Dietitian, Professional Dietitian and Dietitian are protected by law under both the 1991 Regulated Health Professionals Act and the Dietetics Act of Ontario.
By definition all dietitians are nutritionists given that their education, training and area of expertise is nutrition but not all nutritionists are dietitians. This is because dietitians have met national standards for education and training and are members of a regulatory body; in Ontario it’s the College of Dietitians of Ontario. Dietitians are regulated in the same way medical doctors, dentists, nurses, massage therapists, optometrists, physiotherapists etc. are.
The term nutritionist is not protected by law so people with different levels of education and knowledge can call themselves a ‘nutritionist’. Some provinces (Alberta, Quebec and Nova Scotia) have legally protected the title Nutritionist or Registered Nutritionist but in Ontario, the title ‘nutritionist’ is not regulated. Be sure to ask for clarification about education, training and clinical experience when seeking out nutritional advice.
A dietitian is an expert in food and nutrition; they use this expertise to promote health & well-being and to reduce the risk for, and manage disease by assessing, diagnosing, and treating dietary and nutrition-related problems, including promoting weight loss in a healthy, controlled manner backed by scientific evidence.