You can take the PN cert to learn about nutrition if you don’t want to go to school, but it is not equal to going to school and being a real nutrition professional such as a registered and licensed dietitian or a CNS (they require extensive science work and a graduate degree and some sort of supervised practice, like an RD, but they are a minority yet still a legit credential). The training you have to complete to be an RD or CNS (both can get licensed) is just like that of any medical professional but they just do nutrition. Like others have said, PN does great with marketing and getting gyms to count it as a credential that raises pay, but it honestly has no merit for getting you a job in nutrition and you will lack credibility against the 80k+ RDs. You will be competing against people who are RDs who are looking for jobs, people who completed a BS in nutrition and are looking for jobs, dietetic technicians, etc. There are a lot more of them than there are people who have the cash to pay $1000 to John Berardi’s new certification who are likely more qualified.
Those who say that RDs only have medical nutrition training must not be familiar with the program. There are many rotations. 8 weeks are clinical in the hospital, but there are community, counseling, private practice, sports nutrition rotations as well. There is also a CSSD credential for those who have 1500 hours of work in sports nutrition and eating disorders. To go into the field of nutrition and not know when you are working with an eating disorder is not good for the client and puts you at very high liability.