James 'Arg' Argent fears he could "die" if he doesn't lose weight.
The 31-year-old star has ballooned to 24 stone, and while he has been for check-ups at the doctor, he worries he may "become ill or die" if he doesn't shed some pounds.
James said: "I've had check-ups. My heart's OK, I have no signs of diabetes and my cholesterol is not too high.
"But I was weighed and I was the biggest I'd ever been - around 24 stone. I could become ill or die."
Arg is set to swim the Channel, from England to France, as part of a new Stand Up to Cancer show, 'Sink or Swim', and he is hoping the big challenge will "kick-start" his weight-loss.
He added to The Sun newspaper's Bizarre TV column: "The swim is an opportunity to sort my life out.
"I need to lose about eight stone or more. I've got a long way to go even after I swim the Channel. But it's just a perfect way to kick-start my healthy weight loss.
"I get a bit of stick on social media for my size. You try to be thick-skinned but it does affect you."
Earlier this month, Arg turned to boxing champion Tyson Fury in a bid to lose weight.
A source recently said: "He has asked Tyson if he can help him shift the pounds because if he doesn't do something drastic, his health is at risk.
"He is great friends with Tyson, and he has agreed to help him out. Arg gets on much better when he is doing something he enjoys, like being in a boxing gym.
"Tyson has said he can give him tips and advice to train efficiently. He said diet and discipline was a key factor and that is where Arg really needs to sort himself out."
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