He's 'on a diet'. [=he is eating less food or only particular kinds of food in order to lose weight]
Environmental changes are depriving the birds of the insects that form their 'staple diet'.
We've been given a steady 'diet of' political scandals in recent months.
(..) How about a Grasshopper? I make a mean Grasshopper. Okay? Good, coming up. - Sheldon, what are you gonna have? - I'll have a Diet Coke. Okay, can you please order a cocktail? I need to practice mixing drinks. Fine. I'll have a virgin Cuba Libre. That's rum and Coke without the rum. Yes. So Coke. Yes. And would you make it diet? There's a can in the fridge. A Cuba Libre traditionally comes in a tall glass with a lime wedge. Then swim to Cuba. Bartenders are supposed (..)2007 TvShow: The Big Bang Theory Title: The Grasshopper Experiment Season: 1 Episode 8