Mrs Forbes, a dental practice manager, said healthy lifestyles seemed the norm in New Zealand.
"We see people out running, jogging and walking. It makes you want to be part of it. We never saw people doing it in England.
Mr Forbes: "New Zealand gives off the atmosphere of fitness."
"We came over as overweight Poms with an appetite for drinking and poor eating.
"This country and its people inspired me and Elaine to get off our bums and get out there and live life," said Mr Forbes, 46, an assistant manager at a technology company.
Heavy drinking, pies, hot chips, pizza, lollies and chocolate were their standard fare in Britain.
On arrival in New Zealand, Mr Forbes weighed 121kg but is now 92kg. His wife, 45, has shrunk from 63kg to 46kg.
Even a health scare in the UK hadn't shocked Mr Forbes into healthier living.
"I got a stent fitted in my heart 11 years ago [to widen a narrowed artery]. Just after that I got diabetes. I've got high blood pressure and high cholesterol," he said.
But in 2009 he met a personal trainer, which set the couple on a path to where they now exercise for at least 90 minutes a day, they run quarter marathons, Mrs Forbes has dropped from size 14 to six, junk food is banished from their lives, Mr Forbes has lost his dreaded "man-boobs" and is preparing to contest his first body-building competition next month. He has also been able to reduce his medicine dosages.
Mrs Forbes said friends in Britain were shocked by new pictures of the couple.
"They didn't recognise us."