A Registered Dietitian is a diet, food and nutrition expert who has met academic and professional requirements including:

• Earned a bachelor's degree with course work approved by the Academy of Nutrition and Dietetics' Accreditation Council for Education in Nutrition and Dietetics (ACEND). Coursework typically includes food and nutrition sciences, foodservice systems management, business, economics, computer science, sociology, biochemistry, physiology, microbiology and chemistry.
• Completed an accredited, supervised practice program.
• Passed a national examination administered by the Commission on Dietetic Registration.
• Completes continuing professional educational requirements to maintain registration.

 Academy of Nutrition and Dietetics/American  Dietetic Association   

Registered Dietitian vs Nutritionist

A nutritionist is NOT A registered dietitian. Virtually anyone can call him- or herself a "nutritionist" regardless of education or training.

The "RD" credential is a legally protected title that can only be used by practitioners who have fulfilled the above requirements and are authorized by the Commission on Dietetic Registration of the Academy of Nutrition and Dietetics.