Yes, definitely meat because it’s something most people eat everyday, unlike carrots, or apples, for example.
My husband always tells me that the point is to give up something you really enjoy, so it doesn’t have to be meat. Meat would not work if you’re a vegetarian, for instance. The other thing he tells me, is instead of giving something up, you can take something on. Like, say a rosary (if you don’t normally do that), go to a daily mass after work, etc.
I find that at work, we would always go to Team Lunches only on Fridays, and many restaurants close by did not have vegetarian dishes (or they’d have seafood, which I am not a fan of), so I would have to eat meat. This is the case where you can give something else up, or taking something on instead.