Great question!
Nutritionist is an unregulated term. Anyone, including your friend who has a career in something completely different can call themselves a nutritionist. While some "nutritionists" may hold certifications, it's not required so even you could call yourself a nutritionist as someone who is interested in nutrition.
A registered dietitian (RD) is someone who has completed and maintains rigorous educational and training requirements.
At a minimum, a registered dietitian completes:
· A bachelor’s degree, including a Didactic Program in Dietetics- some RD's even have master's degrees
· 1200 hours of supervised practice
· A registration exam
· 75 hours of continuing education every 5 years
RD's only use scientifically based research methods for disease control and prevention, improve relationship with food and body image, improvement of athletic performance, and help increase food quality. So we could say that a registered dietitian is a nutritionist, but a nutritionist is NOT a dietitian. In fact, some dietitians call themselves registered dietitian nutritionists (RDN)- it's the same thing as a registered dietitian just with an extra letter! How's that for confusing?!