Both terms are used interchangeably but can mean very different things. I for one do not have a preference of what I am called: nutritionist, dietitian, and food lady what have you but there is a point of differentiation that is worth discussing to help an individual decide who is best to work with.
A dietitian must have a bachelor of science in nutrition or dietetics from an accredited school and enter a post graduate internship program that usually lasts nine months to a year. In the internship program the individual will work in a hospital, medical institution, government, or community focusing on medical nutrition therapy. After completing the required hours in the internship, that individual is then able to sit for the national registration exam governed by the American Dietetic Association. Once passed most states require licensure and the dietitian is required to take at least fifteen continuing education credits a year to maintain their registration and licensure.
A nutritionist is not governed or accredited. Essentially anyone who is interested in health, fitness, or nutrition can call themselves a nutritionist. This is not to say that the nutritionist does not have personal experience or some training and knowledge of the subject, it just means they are not governed by a national governing body and most likely did not work in an internship dealing directly with individuals and different disease states that present themselves in medical nutrition therapy.
Most physicians will refer patients to a registered dietitian as they have specific medical nutrition therapy experience. Also registered dietitian’s can work with insurances as nutritionists can not. To find out if you are working with a dietitian or nutritionist you can always ask for the individual’s accreditations and you can also look for the acronyms behind the name. RD means registered dietitian and LD means licensed dietitian. Some states have a LDN meaning licensed dietitian and nutritionist. You can also ask the individual for their registration number and check with the American Dietetic Association.
Your insurance company can usually guide you to a registered dietitian in your area as well as the American Dietetic Association at http://www.eatright.org/. Good luck and be well.