IPA: //daɪˈɛtɪʃən//
KK: /daɪˈɛtɪʃən/
A professional who is trained to advise people on what to eat in order to lead a healthy lifestyle or achieve specific health goals.
She consulted a dietician to help her create a balanced meal plan.
Dietician → It is formed from "diaita" (from Greek, meaning way of life or diet) and "-ician" (meaning a specialist or practitioner). A dietician is a specialist in the way of life related to food and nutrition.
Think of a 'way of life' ('diaita') focused on food and nutrition, which is what a dietician specializes in.