The 38-year-old from Sunderland shed 12st, 12lbs since the beginning of the series, which is a 40% weight loss.
Presenter Davina McCall and trainers Richard Callender, Rob Edmond and Charlotte Ord joined him as he won the show, along with the rest of the former contestants.
Kevin beat his fellow finalists Amy McLernon (who lost 6st, 3lbs) and Sarah Partridge (who lost 5st, 8lbs).
After being crowned the winner, Kevin said: "I can't believe it, everything I've done since the minute I applied for the show has led me to this moment and it feels incredible.
"I came to The Biggest Loser as the heaviest person ever to compete in the programme and that gave me massive motivation to shed that title and chase the title of The Biggest Loser."
McCall said of his victory: "Kevin's a worthy winner because right from the beginning he took everything that Biggest Loser had to offer and made that into something that he could take away and use; and not just for the mere eight weeks that he was there but for the rest of his life.
"I really believe that for Kevin this weight loss isn't just for the programme it is for the rest of his life and he's a winner in this series and in life."
Kevin added: "I think there's so many things that I have learnt, not just about diet and exercise but about myself. For me it isn't about the prize and the plaudits it's about winning and what that means, which is that I have lost a massive amount of weight and becoming fit and healthy.
"Being able to show others that if I can change my life, they can. If I can inspire just one person to do what I have done, and truly make a change I will be a happy man."
Trainer Richard Callender said: "Kevin was someone who I realised from the start had so much untapped potential to not only become a contender, but someone who could become The Biggest Loser. I'm incredibly proud of him."
Kevin McLernon takes home £25,000, while runner-up Jessie St. John Sharpe - who lost a total of 7st, 8lbs - won a week-long holiday to Antigua.