People have various "bumper lines," i.e., limits to which types of food or drink they're willing to bumper.
True "bumpering" is done regardless of whether the bumperer has money or is hungry. It's a principle-based practice to avoid wasting food. But hunger or poverty can also be major motivators.
"Go bumper it bro!"
"Hey man, check out this sandwich I got."
"Is that a double burger with only one bite taken out?"
"Oh man, what an excellent bumper."
"You want some of this soda I bumpered?"
"No man, drinks are past my bumper lines."
Used in parts of Australia as a noun ("You're a bumper, mate!") and occasionally as an adjective, e.g "He supports a bumper football team."
"He's too much of a bumper to ever work that out!"
"Only a bumper wouldn't be able to do that."
"That's a bumper thing to do!"