Former MMA star Chael Sonnen claims he once lost 8kg in just 22 hours to make weight after agreeing to a fight on short notice.
The ex-UFC and Bellator fighter told former NFL punter Pat McAfee on his podcast about the drastic weight loss, which was sparked by needing to shed 16.5kg in 20 days.
"This is one of the most difficult things I've ever done in my life," Sonnen said. "I got a call on short notice, I was headed to the gym, and they said, 'Hey, can you fight in 21 days?'
"Well that means the weigh-in was in 20 days. I said yes but when I got to the gym the first thing I did was I got on the scale and I was 36.2 pounds (16.5kg) over.
"This was a very daunting task — just over 36 pounds in 20 days.
"I got it off. This is 10 years ago, I remember it like it was yesterday."
The day before the weigh-in, Sonnen still had plenty of work to do but miraculously, he got the job done.
"I had to lose 17 pounds (8kg) in 22 hours," Sonnen said.
"Now that said, I was fully hydrated and there are even things you do with the water load to try and lose weight, where you will drink a lot, three gallons (11 litres) in one day, for example, of water.
"You do sweat very easily and so 17 pounds maybe wasn't quite as hard as it sounds like it was, but those final five pounds (2kg) were sure difficult."
McAfee was visibly shocked.
"Seventeen pounds is not that difficult? I mean, I couldn't lose 17 pounds in six months," he said.
Lots of fighters will roast themselves in a sauna or sweat the weight off by running while wearing heavy tracksuits, but Sonnen said a "new trick" a bodybuilder taught him was the best way to get lighter quickly.
It involves a hot bath and lots of salt.
"You need that water hot, you cover your body in what's called Albolene. That's just a make-up remover but it opens up your pores, and then your pour four bags of Epsom salt (in)," Sonnen said.
"That's the real trick to this is the salt. You go sit in the salt and just like a slug that salt will pull that water out of you.
"It will drain you like you wouldn't believe. You won't have any energy, it's very difficult."