They admit it isn't actual scientific proof but these Australian radio hosts believe they've finally shown the Big Mac has gotten smaller.
The Collective Noun hosts had a listener find an Australian McDonald's ad from the 1990s and came up with the perfect plan to compare sizes.
They'd track down the ad's star, 90s country music icon James Blundell, and get him to recreate the shot.
The Hit Network hosts Zach Mander and Dom Fay found Mr Blundell at the Gympie Music Muster but realised there was no McDonald's in the town so had to travel 40 minutes to get one.
"I haven't had a Big Mac in 20 years, if I order one today will it be the same one I had 20 years ago?," Fander asks in the drive-through.
"Possibly. I wasn't alive 20 years ago so I'm not sure," chuckles the attendant.
When they finally get to Blundell they sit down to give him the burger.
"It was a proper handful, it was a big handful," he recounts of the ad.
Comparing images back in the studio, the new Big Mac does look considerably smaller than the old one.
But the hosts admit it was cold by the time they got it to Blundell.
"It's irrefutable," they joke at the end of the video they shared about the discovery.
However, a McDonald's spokesperson has told the Herald that the Big Mac hasn't changed in size over time.
"The Big Mac hasn't changed size, but we definitely show our products in a more realistic way in our advertising than we did 20-30 years ago which is why the Big Mac we see today looks different to the Australian advertisement in question."