I bet they do know it.
I bet there's an online community somewhere with several hundred competitive mayonnaise eaters.
Edit: Yup. I guess this needs some kind of warning. Don't click if you don't want to see someone empty multiple big jars of mayonnaise with a spoon in under 3 minutes. https://www.youtube.com/watch?v=_INKqoqDYsk&t=232s
I highly suspect it comes out the other end shortly after being ingested. Unless there are rules against that or something. Somehow, I feel like the mayo-eating professionals aren't exactly well regulated.
Hey just wanted to remind you about that mayonnaise video when you read this. Give in to the morbid curiosity. The call of the void burns for you concede and watch the video in full. See how gross it really is for yourself.
Ok, sure, that's a lot of mayo. But I didn't think OP was referring to an amount consumed in one sitting. Surely there's someone out there that just loves macaroni salad or coleslaw who ends up eating way more on a longer timescale.