I cannot imagine that any health coach certification can stand on its own regardless of the context in which you want to provide services.
If it is in the medical field, you would need specific credentials for that. And in the fitness field, your recommendations are usually generically about nutrition (unless you have a credential there) or about exercise. While the ACE Health Coach certification talks about exercise a good deal, it is not specific enough to develop a solid exercise program.
To me, this certification is only complementary to and an integral part of my personal training.