Mr Ryall said the contract was part of a nationwide initiative worth $40 million and expected to reach 900,000 people.
"We looked around the world for a programme which had people actually taking responsibility for themselves, their families and their community to live healthier lives and lose weight," he said.
They found that programme in Australia - Healthy Together Victoria.
"Research showed the kids in that state were 1kg lighter, measured an inch (2.5cm) less around the waist and could run faster. This was unparalleled with every other effort to reduce obesity," Mr Ryall said.
The programme would be rolled out across 10 communities and Wanganui was the first contract announced.
He said Te Oranganui would bring together a number of groups, including Sport Wanganui, and encourage early childhood centres, schools, workplaces and sports clubs to adopt more healthy focused efforts.
"They will employ skilled health promoters who will go out into the community and will teach people to do more healthy things.
"They could go into sports clubs and help them reformulate the menus they might be offering over the bar, or they could go into early childhood centres and encourage children to have more water and fruit.
"It's about a lot of things happening on a big scale in the community and it's this approach which has generated those results in Victoria."
Mr Ryall said obesity wouldn't change by the Government making laws, it would only happen with people taking responsibility.
"That's what this programme is about. If it works as well here as in Victoria, it will be a game-changer."
The programme would also focus on unsafe alcohol use and smoking. He expected Te Oranganui would start recruiting health promoters in the next few months.
Whanganui MP Chester Borrows welcomed the news.
"Obesity is a major health challenge. Having Te Oranganui, a proven provider, is great news for Wanganui," he said.
