The others have given you some insight to other certs and scope of practice as personal trainers, but have you ever considered a health coach or behavior modification cert? I’ve found this to be very helpful in helping clients to make healthy habits a part of their lives–both with nutrition and exercise together. Most people know they need to eat healthy, but many need the tools, education, and support to make actual changes in their lifestyles.
Just a thought… I know the nutrition piece can be tricky as personal trainers.
Best to you whatever you decide!