I am a certified health coach, but I want to see what other titles I am allowed to put on marketing materials.

This isn't an IP question, it's a matter of state statute. You'll need to hire a local lawyer to see what your business & professions code says about regulation of your profession, including what you're allowed to call yourself in marketing materials. Disclaimer: I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.

You need to be careful how your represent yourslef to avoid any confusion or ethical violations. You should note that a Registered Dietitian (RD) is a uniquely qualified nutrition expert. Every individual with this credential has completed a four-year degree that includes science-based curriculum approved by the Commission on Accreditation for Dietetics Education (CADE). One must also complete a demanding dietetic internship which range in duration and format but are accredited by the CADE. Dietetic interns must complete a minimum of up to 1200 hours in the field of dietetics before qualifying to sit for a national exam. Only after completing these requirements can an individual be credentialed as an RD by the Commission on Dietetic Registration. To maintain the RD credential, one must complete a minimum number of continuing education courses every five years. Titles such as “Nutritionist” or “Health Coach,” do not guarantee that the individual has the training and education in the science of nutrition or is required to follow any standards of conduct required by a “Registered Dietitian.” Importantly, you should only advertise or represent yourself as "certified" or "registered" if you have been so acknowledged by a certification or registration body within your state or federally to avoid any potential confusion or potential misrepresentation. Good luck. Disclaimer: This answer does not establish an attorney-client relationship and does not constitute legal advice. It is for general information purposes only.

Check with your state's department of professional regulations. This is not an IP question