Some people like to brag about their "credentials", which to my mind is an indication of their immaturity.
It is also highly unlikely that this person has any inkling as to the knowledge attained by other health professionals and laypersons in the fast and the fasting process, gleaned from decades of hands-on experience.
Many Alternative and especially traditionally qualified medical personnel, are usually totally ignorant of this subject, but will display their "knowledge" as being both autocratic and authoritative: which of course it isn't.