Spencer Matthews has lost nearly two stone after burning more than 7,000 calories a day during his "extreme" 30 marathons in 30 days challenge.
The former 'Made in Chelsea' star is taking part in the epic task across the Jordanian desert in the peak of summer for Global’s Make Some Noise charity, and it has resulted in him shedding more than 10 kilos in weight.
Speaking on Heart Breakfast with Jamie Theakston and Zoe Hardman, he said: "I’ve lost over 10 kilos now. This is not how I would advise people to try and lose weight
"What we’re doing out here is quite extreme.
"Weight loss is certainly not really a point of this, but I’m burning over 7,000 calories a day, so to replace those calories is actually quite difficult in itself.
"Obviously, we’re quite tired during the day, it’s very, very hot out here, so you’re just constantly expensing energy. And yeah, I mean, I’m a hungry boy, and I love my food – but 7,000 calories is quite rough on replace, so I am getting smaller
"But the body is a really amazing thing; it kind of adapts to where you are, what you’re doing, what your circumstances might be.
"I think at this stage, having run 24 consecutive marathons, my body has gone, ‘Christ, you might just carry on doing this!’ So it does just chuck off muscle.
"I came in much heavier on top, and I have lost most of my muscle, so there we go."
At one point during his epic challenge, Spencer admitted he was "very lucky" to avoid stepping on a venomous horned viper snake, which can kill a human in less than five minutes.
He said: "I very nearly trod on a horned viper. I don’t want to over dramatize the situation, because of course nothing happened, but I didn’t see it.
"I was running a tyre track through the desert, and this thing is quite well camouflaged, and I accidentally ran over it.
"The bloke behind me, Johnny, noticed it and stopped that there was a snake, and I turned around and looked at it.
"It turns out this thing kills a camel in five minutes and can kill a human far faster than that.
"I just want to reiterate that it didn’t attack us or anything like that, so I’m not pretending it did.
"But we were right next to it, I was quite lucky not to tread on it. I did run over it, literally, but I didn’t tread on it.
"There’s no anti-venom for horned vipers – and this is all cleated by our doctor – and the local Bedouins love to emphasise a bit of a story from time to time, so they were like, ‘If this thing bites you, you’re dead.’
"That’s not quite true, there are a few things you can do."
Spencer Matthews is running 30 marathons in 30 days across the Jordanian desert in the peak of summer for Global’s Make Some Noise charity. Head over to Global’s Make Some Noise website - https://spencer-matthews-challenge.raiselysite.com/ - to donate.
Tune into Heart Breakfast with Jamie Theakston and Amanda Holden weekdays from 6:30am – 10:00am, also on Global Player