A nutritionist is a person who advises on matters of food and nutrition impacts on health. Different professional terms are used in different countries, employment settings and contexts — some examples include: nutrition scientist, public health nutritionist, dietitian-nutritionist, clinical nutritionist, and sports nutritionist.
Regulation of the title "nutritionist"
Some confuse the terms "dietitian" and "nutritionist," and this tends to be erroneous. However in many countries and jurisdictions, the title "nutritionist" is not subject to professional regulation; any person may call themselves a nutrition expert even if they are wholly self-taught. In most US states, parts of Canada, Australia, and the United Kingdom, the term nutritionist is not legally protected, whereas the title of dietitian can be used only by those who have met specified professional requirements. One career counselor attempting to describe the difference between the two professions to Canadian students suggested "all dietitians are nutritionists, but not all nutritionists are dietitians."
The term nutritionist used to be associated with alternative medicine. Prominent examples include Gillian McKeith and Robert O. Young. However, there are a large number of practising nutritionists without appropriate qualifications to be a potential danger to the general public. A demonstration of the ease in which it is possible to become an accredited nutritionist can be seen in Dr Ben Goldacre's successful application to have his dead cat Hettie accredited as a certified professional member of the American Association of Nutritional Consultants (the organisation by which Gillian McKeith is accredited). A key danger is that many of these unqualified nutritionists can be seen on the World Wide Web to contribute to online health discussions by advising a person to ignore their doctors' prescription (that opinion being the considered opinion of a qualified scientist) in favour of some "fad" foodstuff which they claim will cure all ills. Nutritionism, practiced in a responsible way by a qualified person could be a robust scientific discipline, which uses science to formulate guidelines if it were not for the overwhelming numbers of unqualified practitioners. The Association for Nutrition operates a register of nutritionists and accredits Registered Nutritionists who have a verified background in nutrition research and training and Associate Nutritionists who have graduated from courses accredited by the Association.
The title "nutritionist" is protected by provincial law in Quebec, and Nova Scotia. The term "Registered Nutritionist" is protected in Alberta. The term “Registered Dietitian/Nutritionist” is protected by law in New Brunswick.
For example, the Nova Scotia Dietetic Association is the regulatory body for professional dietitians and nutritionists in that province, authorized by legislation, the Professional Dietitians Act, "to engage in registration, quality assurance, and when necessary, the discipline of dietitians in Nova Scotia to ensure safe, ethical and competent dietetic practice." Professional requirements include a Bachelor's Degree in Dietetics/Nutrition from an accredited university, a program of practical training, and successful completion of a registration examination (the "Canadian Dietetic Registration Examination" or CDRE).
In Morocco, "Nutritionist" is a protected title and might refer to a researcher in the field of nutrition or to a person who practices therapeutic nutrition. To hold the title of Nutritionist, a person should have carried doctoral studies in the field of nutrition and obtained a Ph.D.
On the other hand, the title of "Dietitian" is given to whoever carries studies in nutrition schools for 3 years and obtains a B.Sc. However, unlike nutritionists, dietitians are not given authorizations to open private offices and to practice.
In South Africa, nutritionists must be registered with the Health Professions Council of South Africa. The Council regulates the professional titles of "Nutritionist", "Student Nutritionist", and "Supplementary Nutritionist", along with "Dietitian", "Student Dietitian", and Supplementary Dietitian". Requirements for eligibility for registration include a recognized Bachelor's degree from an accredited educational institution. The undergraduate training should include the three practice areas of therapeutic nutrition, community nutrition, and food service management.
"Nutritionist" is not a protected term in the UK, unlike "dietitian"; the latter must be registered with the Health and Care Professions Council. The Association for Nutrition  is a registered charity that holds the UK Voluntary Register of Nutritionists (UKVRN). Its purpose is to "Protect and benefit the public by defining and advancing standards of evidence-based practice across the field of nutrition and at all levels within the workforce". All registrants on the UKVRN have had to provide evidence of their training and professional nutrition experience. They have also committed to abide by a Standard of Ethics, Conduct and Performance. There are three categories of UKVRN registrants, Registered Nutritionist (RNutr) with nutrition specialism in public health, nutrition science, sport & exercise, food or animal nutrition, Associate Nutritionist (ANutr) and Fellow of AfN (FAfN).
The Association for Nutrition and the UKVRN is acknowledged by Public Health England, NHS Careers, NHS Choices  and the National Careers Service  as the professional body for nutritionists in the UK.
Associate Nutritionists (ANutr) are recent graduates, who have been able to demonstrate a sound foundation of knowledge and understanding in nutrition science, and are working towards gaining sufficient experience within a specialist area to become a Registered Nutritionist (RNutr).
Registered Nutritionists (RNutr) have been assessed as having demonstrated that they have met rigorously applied knowledge, understanding and practice core competencies. They commit to keeping their knowledge up to date and ensuring they follow evidence-based practice.
Fellows of the Association for Nutrition (FAfN) have been Registered Nutritionists (RNutr) for at least five years and have been recognised by their peers to have made a significant and sustained contribution to the advancement of nutrition practice, research or education at a national or international level.
Since 2002, the number of jobs for nutritionists has reportedly grown faster in the National Health Service (NHS) than in any other sector. Despite it being recognized that nutritionists have an increasingly important role to play in health care in the UK, the NHS employs fewer dietitians each year and the profession itself is shrinking.
Dietitians and nutritionists in India held about 150,000 jobs in 2011. More than half of all Dietitians and nutritionists worked in hospitals, nursing homes, and physician's offices and clinics.
The need for Dietitians and nutritionists is increasing every day with sedentary lifestyles, high consumption of fast food and other food related health disorders at an all-time high. They also help to reduce the resistance for diseases, such as malaria, by providing diets rich in protein and calories. Dietitians and nutritionists can find employment in hospitals, fitness centres, spas, health clubs, colleges, nursing care facilities, canteens, hotels, government, etc. One can also work as consultants or do private practice.
Several professional associations are available to serve Nutritionists, Dietitians, and Food technologists in India e.g. Nutrition Society of India, Food Scientists and Nutritionists Association India, Indian Dietetic Association, IAPEN  etc.
To obtain the Nutritionist title, one must have studied at a recognized university for four years plus a year practice (internship). The Nutritionists are registered at the Conselho Regional de Nutricao. A Nutritionist can prescribe diets, work at hospitals, with clinical intervention, or in food production segment.
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- Goldacre, Ben. Bad Science. (also published in The Guardian newspaper)
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- The Society for Clinical Nutrition and Metabolism