Niche down. You are waaaay to broad in your target market right now. And please provide more information in your question: a single sentence is not enough to get a complete answer from an expert.
> WHO are you planning to serve?
> WHAT problem situation(s) are they in now that demand(s) your help to get them of?
> WHY should they choose you over some other, similar consultant?
> What RESULTS can they expect from working with you that are astonishing and effective?
Answering these questions will help you considerably with your targeting and marketing message.
On top of what Jason explained, which are the basics for starting any business, based on understanding who your audience is, you need to figure out where they are? How do they get information on the topics you are hoping to consult them on right now? Who is providing that information? Why are they listening to those individuals right now? Only by answering those questions are you able to target your audience and reach through the noise that is being presented to them today.
The first thing I suggest is to test the market. Go out there and see who you can help as a nutritional counselor. Start with your warm market. Treat this as you would an MLM opportunity.
Make a list of people contact them and see how they are. Ask them if they know anyone that could use guidance in improving their health. They may just say they're in need.
Hope that helped. Feel free to connect and explore more in a call.
All the best,