Charlie Rudd caused an upset at the recent Battle of the Belts charity boxing match in Palmerston North.
The match was held to raise awareness for obesity and diabetes and sold close to 1000 tickets.
Rudd, 41, from Paraparaumu, who only started boxing for the first time in December, revealed this was a fight close to his heart.
In 2008, after a wrist injury during a rugby match, Rudd weighed 117kg.
"It was so bad, I couldn't breathe, but the worst thing of all was I couldn't do things with my kids.
"And my mum was diagnosed with diabetes, so this was the right fight for me."
He weighed in for the fight at 89.9kg.
Rudd began to turn things around in 2009 by surrounding himself with people who enjoyed fitness, and starting a programme of body building.
Jimi Perica, Rudd's coach, said it was clear Rudd was the underdog in this match.
His opponent, David Silk, had five fights under his belt and had home turf advantage.
But Rudd had a secret weapon.
His mother, Anawarihi, flew from Brisbane to support her son and stood ringside throughout the fight.
After the third and final round, Rudd was declared the winner by unanimous decision.
As he exited the ring, he went straight to his mother, and handed her the trophy, and explained that she was the most influential person in my his life and that this win was for her.
"Charlie worked really hard, stayed focused and paced himself," Perica, who runs Jimi's Boxing Club in Kapiti, said.
"He deserves this win and we are happy to have the trophy brought home to Kapiti."
Rudd expressed the hope that his participating in the fight, would challenge others to get out of their comfort zone and put their health first.
"If I can do it, anyone can do it."