a diet supplement的用法和样例：
- For example, carnitine is often sold both as a bodybuilding supplement and as a diet supplement, whereas the "andro" supplements are generally kept exclusively in the bodybuilding arena.
- The Irish used to live on a diet of potatoes.
- The doctor says I've got to go on a diet.
- He is on a diet to reduce some weight.
- No chocolate, please. I'm on a diet.