The stretchers mean staff don't have to physically lift overweight patients into the back of the van. St John records an average of eight to 10 injuries a month from lifting and handling patients.
Police Association president Chris Cahill said it was a relief to see new equipment, as handcuffs were one of the most important tools to keep police staff safe.
"If you can get a handcuff on someone, you can control them.
"But lately getting that handcuff on in the first place has been increasingly troubling.
"If someone doesn't want to keep their hands still, it can be incredibly hard to make them.
"So if you can get cuffs on quickly and easily it certainly takes a lot of the risk out of dealing with them."
Police operations manager Inspector Paris Razos said standard equipment just wasn't working the way it had in the past.
The new handcuffs were more expensive, with a per unit cost of $73.79, compared with the previous per unit cost of $57.17.
But Inspector Razos said the cost was worth it to ensure the health and safety of officers, as well as the comfort of the person being restrained.
"It can make an awful lot of difference when it comes to the officer's ability to restrain someone who may be struggling.
"Many sections of the community are getting physically bigger, and therefore we have to be at the sharp end of that to make sure we're prepared.
"The cultural make-up of New Zealand means we have certain races here who are genetically larger than other races.
"So having a growing population of certain ethnic groups, that may also be a factor in this."
Massey University demographer Professor Paul Spoonley believed the changes were just the first signs of adjustments that would be needed across our society.
"The police are at the cutting edge of some of the negative social changes, because they often work with people with low socioeconomic status.
"We're also seeing impacts in schools, impacts on public transport where they have to cater for larger people, and the healthcare system is another institution where they're having to contend with much larger people who have chronic illness."
Professor Spoonley warned that a growing number of obese people would soon struggle to access core public service.
"Either they can't get there, or the services themselves don't provide for them.
"Our core systems, justice, education, and health, are going to have to gear up to deal with people who are much larger and have more chronic illnesses."
Upgrading for the obese
• 251 new police handcuffs ordered at $73.79 each
• Old police handcuffs were $57.17 each
• Police considering replacing custody gowns and blankets
• 43 ambulances upgraded with electric stretchers so staff don't have to lift overweight patients. At a cost of $8.6 million
Adult obesity
• Almost one in three adults are obese (32%)
• A further 35% of adults are overweight but not obese
• Adults living in the most deprived areas are 1.7 times as likely to be obese
• The adult obesity rate increased to 32% in 2015/16, from 27% in 2006/7
Childhood obesity
• One in nine children are obese (11%)
• A further 21% of children are overweight but not obese
• Children living in the most deprived areas are three times as likely to be obese
• Child obesity increased to 11% in 2014/15, from 8% in 2006/7
(Source: Ministry of Health New Zealand, Key Results 2015/16)