Early in the morning at Genetics Gym the floor shakes as the "Big Boys" hit the cardio fitness sessions.

They sweat it out for 90 minutes with press-ups, circle boxing, running, sprints and more.

Gym owner and trainer Buck Stowers has developed the Big Boys programme and says each session is different. It's aimed at helping big boys lose weight through the right exercise, menu plans based around nutrition and a supportive team environment.

"These guys motivate each other – not once in the last six months have I heard I can't do it," he says.

Mr Stowers has had leaders of the community come to him for help to lose weight. He gets doctors' referrals and people who tell him they're at risk of dying because of their weight.

He runs the sessions with trainer Darren Steele and at the end of each there's a weigh-in and a debrief.

Dr Sam Fuimaono says it's all about diet and exercise and it's not "rocket science".

"But a lot of us struggle to exercise on our own," he says.

When he started with Big Boys he weighed 182kg and is now down to 135kg.

Other men going to the classes are losing significant amounts of weight like Bob Sila who has dropped from 220kg to 139kg.

Alan Va'a says working with others on the programme has had a tremendous impact on him.

"It's still a fight for life for me," he says.

Mr Stowers, who owns the gym with his wife Lucretia, had the idea for a Big Boys club about seven years ago after discussing his concerns about obesity in the community with Su'a William Sio, now Mangere's MP.

"This is about loving yourself enough to do something – it's not a quick fix," Mr Sio says.

Classes start as an initial 12-week programme with the aim of getting people to the point where they're self-sufficient and don't need the trainers. Big Girls classes are also available.

Classes for Genetics Gym members cost $13 a session. Call 262-3686 for information.

- © Fairfax NZ News