Registered Dietitian has:

• Completed a minimum of a bachelor's degree program approved by the Commission on Accreditation for Dietetics Education (CADE)
• Completed pre-professional experience approved by CADE
• Passed a national examination administered by the Commission on Dietetic Registration (CDR)
• Completed continuing professional education requirements

A Licensed Dietitian has:

• A bachelor's or graduate degree with major in human nutrition, food and nutrition, nutrition education, dietetics, or food systems management, or equivalent internship or preplanned professional experience approved by the Texas State Board of Examiners of Dietitians
• Successfully completed an examination administered by CDR

A nutritionist?

Anyone can use the term nutritionist, even without any formal education or training. "Nutritionist" is not a professionally regulated term which means there are no minimum qualifications.