on a diet

Don't go on a diet.(不要节食。)

He has been on a diet for as long as any of his friends can remember.(从他的朋友能记得时开始，他就一直在节食。)

I'm on a diet.(我正在节食中。)

I'm forever on a diet, since I put on weight easily.(我一直在节食，因为我的体重很容易增加。)

I can't eat too much, I'm on a diet.(我不能多吃，我在减肥。)

He has been on a diet for 12 weeks.(他已经持续节食十二周了。)

No. I'm on a diet.(不要了，我在减肥。)

We existed on a diet of rice.(我们靠吃大米过活。)

I'm supposed to go on a diet.(我应该节食。)

People who are on a diet mustn't have chocolate.(正在节食的人不能吃巧克力。)