Meaning of the word "on a diet" in English

What does "on a diet" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

on a diet

US /ɒn ə ˈdaɪ.ət/
UK /ɒn ə ˈdaɪ.ət/

Phrase

following a special plan of eating in order to lose weight or for medical reasons

Example:
I can't eat that cake, I'm on a diet.
She's been on a diet for months and has lost a lot of weight.