The 28-year-old, who won the 2018 series of the ITV2 show with ex-girlfriend Dani Dyer, has signed a professional contract with promoters BOXXER.
Fincham, from Kent, hopes to compete in the light heavyweight division and is being coached by Tyson Fury’s former trainer, Ben Davison.
He is returning to the sport after a stint as an amateur boxer for Eltham ABC aged 14, competing in a total of 26 bouts.
Fincham told the PA news agency: “It’s been a complete lifestyle change.
“There’s no more eating takeaways, there’s no more popping to the pub for a beer with your mates, and when I do go out and socialise I’m drinking Diet Cokes and water.
“So it’s been a lifestyle change for the better and I’m feeling so much better.
“I’m sleeping better, everything is falling into place around training like this, and the intensity of it can only be good for me, so the lifestyle change has been big but for the better.”
Talking about his weight, he said: “I’ve lost probably over half a stone at the minute and I’m only a couple of weeks in. It’s falling off me.”
He joked: “I’m going to be so thin soon I’m going to be coming through the crack of the door.”
Fincham, who revealed he had become a father earlier this year, has embarked on a six-week training camp.
He told PA: “Recently I’ve been struggling with my anxiety but since training twice a day, it’s near enough non-existent.
“Exercising every day has made me feel a thousand times better.”
Fincham said he wanted to prove to the public there was another side to him.
He said: “When I get in a boxing ring I’m very focused, I know I’m there to do a job and I’ll do anything I can to win.
“I think the main thing for me is I want to prove a lot of people wrong and I want to show people another side to me – not the dad bod side.
“I want to show them the athletic side of me and I did actually have a talent for boxing and I want to show people that you can go and get yourself in shape and that you can do it.
“And also prove to myself that I can still do it, this is a very personal goal of mine and I just want to show people that I can do it.”
Trainer Davison, 27, has previously worked with world champion Billy Joe Saunders and is credited with helping Fury lose 10 stone ahead of his well-publicised return to boxing.
“The word I can use is an honour and I feel lucky to even be in the gym with him,” Fincham said.
He said he had not spoken to Fury about the sport, but added: “I’d like to. He’s an amazingly talented fighter so I’d love to but I’ve never spoken to him, not in that sense.”
BOXXER founder Ben Shalom said: “We’re really excited about Jack making his professional debut with BOXXER, he resonates well with our audience and brings with him a very credible amateur record.
“He’s a massive personality and I’m looking forward to him shocking a lot of people.’
