IPA: /ˈdaɪtər/
KK: /ˈdaɪtər/
A person who follows a specific eating plan to lose weight or improve health.
She is a dedicated dieter who carefully tracks her meals.
Dieter → The word 'dieter' is formed from 'diet' (from Old French *diete*, meaning a way of life or regimen) and '-er' (meaning a person who). A dieter is a person who follows a specific regimen or way of eating, often for health or weight management purposes.
Think of someone who follows a specific 'regimen' ('diet') — the '-er' just means a person. A dieter is someone who is focused on their eating habits.