I seem to be getting this question a lot lately, so I thought I'd answer it here.
When I tell people I'm an RD, it's often followed by:
Can you make a meal plan for me? What's the best diet book? What supplements should I take? Is dairy bad for me?
All these things play a role in what we do, but really we do SO much more! And the truth is, there is no perfect one-size-fits-all diet or healthy lifestyle.
Our classroom training is in biochemistry, metabolism, anatomy, food science, and more to understand how exactly our bodies digest and use food as fuel.
In order to sit for the RD exam, RDs must receive a bachelor's degree in Nutrition Science. They then go on to complete a supervised practice internship to gain 1200 hours of real world training in:
clinical (hospitals and other medical institutions)
community (private practice or public health)
food service (food safety, food science, production)
long term care (elderly and assisted living populations)
As you can see, we really are a jack of all trades!
Most dietitians do not believe in quick fixes and typically don't care for trendy diets seen in the media. In the private practice/counseling sector we work as coaches and customize dietary recommendations to each client's health needs. Dietitians see a HUGE range of clients and ANYONE can benefit from seeing one! (GI issues, autoimmune diseases, eating disorders, picky eaters, autism spectrum disorders, food allergies, thyroid conditions, prenatal health, athletes, cancer patients, anyone from infants to elderly!)
RDs can also work as food service directors/managers, in school systems, in grocery stores, for food companies, etc.
The 'Registered Dietitian' certification is a national certification. Most states require a separate state licensure as well.
It is important to note that although dietitians are also nutritionists, nutritionists are NOT dietitians. The title 'nutritionist' is not regulated and anyone can (and does) use this term. I have met self-educated people who have developed an interest in nutrition, read a book, and now call themselves a 'nutritionist.' It's great they have such a strong interest in the subject, but it does not necessarily make them a qualified health professional. That's not to say this is all nutritionists - there are some qualified and educated nutritionists out there, however please be sure check their qualifications and education background as there is no standard requirement to use this title.