I graduated from the Institute for Integrative Nutrition in NYC in 2011. I was approached by a person selling an MLM product who said, she was also a health coach. I asked where she went to school... nowhere.
I never made much money because I very quickly recognized that there was no way I would hold someone to a six-month program if they weren't succeeding. Most of my career was working with someone for a couple of sessions, then one-offs if they felt they wanted help developing a routine, or if they wanted my advice on a routine they'd developed.
As an IIN grad, I had a Scope of Practice that outlined what I was able to do. It is definitely 'coaching' not prescribing a diet, exercise plan, or supplement.
I also worked with a physician in helping her patients stay on track with the program she prescribed.
I've also seen coaches stepping far outside their level of training, and it does make me uncomfortable as well.
Having said that, I hate to see you throw the baby out with the bath water. There are terrific health coaches out there. Certification by the International Coaching Foundation is a good place to start.