She's always on a diet—she has issues about food.

她经常节食—她担心吃得太多。

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。

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。

We existed on a diet of rice.

我们靠吃大米过活。

He lived on a diet of junk food.

他把垃圾食品当饭吃。