As hip-hop star Che Fu steps out on stage, the students yell.
Beats are pounding but the musician has a message rather than a song for the Kelston teenagers. The chunky musician - of Niuean and Maori descent - explains that, like many Polynesians, he has been "on the bad side of health issues".
He suggests his fondness for soft drinks might be part of his diagnosis of type-II diabetes, a disease which affects 225,000 New Zealanders. A further 100,000 may unknowingly have the disease.
Che Fu says he once consumed two "one point fives" - 1.5-litre bottles of sugar-sweetened soft drinks, or SSBs - a day. That is getting towards 50 to 60 teaspoons of sugar daily.
One month ago the World Health Organisation issued their widely anticipated guidelines for daily sugar intake.The United Nations agency reiterated its existing guidance that intake should be less than 10 per cent of total energy intake a day, or about 10 to 12 level teaspoons of sugar (one level teaspoon equates to about 4g).
But it went further, and suggested 5 per cent would be better - around 6 teaspoons a day. This is close to American Heart Association advice, which says that to limit weight gain and reduce the risk of heart disease, men should stick to nine teaspoons a day of added sugar, women six and children three.
Depending on how they are calculated, nutrition surveys suggest that New Zealanders consume anywhere between 1.5 and five times the amount recommended by the AHA. Does this matter? Absolutely. The Ministry of Health says the prevalence of diabetes in Maori and Pacific populations is around three times higher than among other New Zealanders. For many people with diabetes, a common factor is obesity. In the view of public health researchers, excessive sugar consumption is a driver of obesity, besides its widely accepted link with tooth decay.
The point Che Fu made to the Kelston boys is echoed in research. The most recent national nutrition surveys found 29 per cent of children consumed four or more SSBs a week. Among Pacific children the figure was 49 per cent, among Maori it was 39 per cent. Another study found children who drank one can a day compared with non-SSB consumers had a mean higher weight of 3.3kg. For those who drank two cans, the figure was 5.3kg.
There is also debate whether sugar is addictive, but the science is far from certain. Beyond that, some research has suggested a link between high SSB intake and cancer, and impaired cognitive development.
Sugar, then, is in the gun and fast becoming the new food battlefield. Where in the 80s and 90s it was salts, fats and carbohydrates, today sugar is the bogeyman.
Researchers and academics in the public health community are mounting a serious push against added sugars in diets. Their target is SSBs. Sensitive to the changing landscape soft drinks giant Coca-Cola has, for the first time, acknowledged that New Zealand, like many countries, has an obesity problem and that its products play a role.
It is making changes, along with other beverage makers like Japanese-owned Frucor, best known for its Just Juice, Pepsi and "V" ranges.
On its website, Frucor estimates that since 2006, when it stopped selling full-sugar drinks at New Zealand schools, it has removed 52.8kg of sugar from the diet of every pupil who might otherwise have had one can of soft drink a day at school.
Beyond health issues, bottom lines are coming into play. Heavyweight European bank Credit Suisse argues that "the global obesity epidemic and related nutritional issues are arguably this century's primary social health concern".
The bank estimates that obesity costs the globe a staggering US$600 billion ($692 billion) a year. Type II diabetes affects 370 million people worldwide, and soaks up 10 per cent of all healthcare costs. With numbers growing at 4 per cent annually, Credit Suisse calculates that by 2020, the annual cost from type II diabetes to the healthcare system globally will be $US700 billion, with nearly 500 million people affected.
Its conclusion - from a bank at the heart of international capital - is that the time has arrived to impose a tax on SSBs.
In its report Sugar Consumption at the Crossroads, the bank concluded: "After balancing arguments in favour and against, we believe that taxation would be the best approach and provide the best outcome: reducing consumption while helping the public sector deal with the growing social and medical costs."
This is the same policy argument which the New Zealand Beverage Guidance Council, a group of public health experts, advocates. The council suggests a tax of 20 per cent, which is double the levy on sweet drinks in Mexico. The Latin American country, the world's most obese nation (more than 70 per cent are overweight), consumes more Coke per head of population than anywhere else. Its new tax, imposed since last October, is a move to turn the tide.
In a small, windowless meeting room, deep inside the sprawling Coca-Cola plant at Mt Wellington, Paul Fitzgerald, the company's general manager in New Zealand, disputes the tax case. He mentions a study that appeared in Health Economics in February, which cast doubt on the idea that hefty tax hike would cut obesity rates.
And, suggests Fitzgerald, because a 20 per cent tax would fall more heavily on the smaller drinks range, larger-size bottles would become more attractive to supermarket shoppers.
"So all we've done is push consumers back to the bigger guy [supermarkets], who'll continue to sell and promote," he says. He has no doubt the tax idea would be regressive and fall more heavily on low income consumers, leading to shifts to cheaper house brands or powdered mixes, with the potential to hurt the business of dairies, who already struggle to compete with supermarkets where 2l Coke bottles can cost as little as $2.
Despite dismissing the tax push, Coca-Cola has nonetheless responded to pressure from public health lobbies and is making changes to its business model. Its critics question whether its new measures are manoeuvres designed to head off any more serious law reforms such as banning children under 15 from buying SSBs to tough advertising restrictions.
Some in the public health sector would go further. A declaration issued after a forum of public health specialists in Auckland on sugary drinks and their alternatives concluded that SSBs should be treated the same as tobacco, and eventually phased out.
When the Weekend Herald met Fitzgerald, he sipped a 250ml bottle of Coke Zero - its smallest sugar-free product. He gestured to the chilled drink, and indicated it was front and centre of the direction Coke was going.
One in three drinks the company sold today were sugar-free, he noted, and cost the same as SSBs. A decade ago, Fitzgerald noted, the figure was one in 10. The company made smaller sizes, sold a wider range of low-kilojoule drinks, put nutritional information on its bottles and cans and supported a nationwide exercise programme which aims to get 100,000 teens active for 60 minutes a day by 2020. By the end of the year, some 5000 vending machines will display nutritional details. The company, which owns one of the world's most visible brands, was careful not to target kids with its marketing and did not sell its full-sugar range at schools.
Though he would not supply the figures, saying they were commercially sensitive, the Coke chief maintained the company was selling a lot less sugar into the community from the entire range of its drinks than it did just a few years ago.
Fitzgerald thinks soft drinks have become a whipping boy in the obesity debate. He parts company with his public health opponents on sugar intake and mentions a study (from the University of Otago), which found while obesity increased between 1997 and 2008, energy intake declined.
"We have a real issue simplifying a debate down to a single product," he complained, when a logical approach would look at added sugars in manufactured foods across entire diets.
"We're just not learning from the mistakes we've made in the past when it was fat, when it was salt ... now it's the demonisation of sugar."
Obesity was undeniably increasing, yet Coke was selling less sugar: "People are looking for solutions and they're jumping on to silver bullets all over the place because it's a hard message to get that [to lose weight] 'I'm going to have to change everything that I'm doing'."
Fitzgerald also bristled at the tobacco analogy: "We find that really irresponsible. There is no safe level of tobacco consumption ... you can't say that about soft drinks. You can consume SSBs as part of a balanced, healthy lifestyle. Putting us in the same bracket as tobacco immediately stops us having the discussions we need."
The Coke chief says he is comfortable having a civil debate around SSBs, but accuses his opponents of using scare tactics to force law changes. He thinks Coke and other soft-drink brands and juices are being targeted as low hanging fruit, when the real issue should be around balanced, exercise and lifestyles.
A few kms away from the Coke plant, Dr Gerhard Sundborn sips an espresso and explains his alter-ego "Dr Fizz (Fighting Sugar in Soft Drinks)".
A public health researcher, Sundborn helped organise the forum which issued the call to eliminate sugary drinks from the food supply. As Dr Fizz, he put on a lab coat, followed Che Fu on to the Kelston stage and urged the teenage boys to quit SSBs. With his hip-hop friend as a warm-up act, Sundborn found it simple to get his message across: quit the stuff or you'll live to regret it.
He says there's a mountain of evidence that SSBs are harmful for individuals - especially children - and costly to society.
One statistic he finds shocking comes from a Ministry of Health report into hospital admissions, which found 5000 children a year under the age of 7 needed a general anaesthetic to get rotten teeth removed, at a cost of $20 million or so.
Sundborn came to the sugar issue from his University of Auckland studies. He says his research supervisors showed him the power of advocacy using the model of the anti-smoking lobby ASH, an influential player in the campaign against tobacco. Fizz wants SSBs gone in New Zealand by 2025 and in the wider Pacific five years later.
Thirty-eight-year-old Sundborn, a part-Tongan father of three, says there are no SSBs at his place. "The kids drink water or unflavoured milk."
He thinks the way forward is by working with the beverage industry - an approach he says doesn't find favour with all his colleagues. Some of them, says Sundborn, are purists who don't trust the industry and suspect pledges to reduce obesity are marketing ploys designed to avoid moves that would threaten sales.
"But I think we've got to be willing to work with industry," he remarked, to have a realistic prospect of achieving the public health objectives.
Coke's Fitzgerald complains about the reception he got at the Fizz forum, where he says he spoke for a few minutes over two days to put the industry case. He felt, he says, like he was in enemy territory.
Political support for the Fizz position is building. Associate Health Minister Tariana Turia recently launched a policy document for the New Zealand Beverage Guidance Panel. The panel aims to set out measures that will reduce SSB consumption. Green MP Kevin Hague, a former District Health Board chief executive, says he backs the idea of a tax on sugary drinks, and would want to see funds raised by a levy spent on prevention work.
Hague was less certain about purchase-age restrictions, saying such measures would need public support to succeed.
For all Coke's fears, and despite pressure from the Fizz declaration, retiring Health Minister Tony Ryall told the Weekend Herald that a new programme called "Healthy Families NZ" was a better, evidence-based way to tackle obesity and poor health.
Ten communities are trialling the scheme, which is based on a successful model used in Australia. Critics of the scheme, however, question whether it goes far enough, and say it needs support with the regulation of industries that impact on health.
Ryall believes the approach he's adopted is the way to go. The Government, he said, "has no intention to introduce more restrictive measures such as sugar taxes, or stricter regulation of advertising".
Countdown to Zero for good of health
A successful but unsung project in South Auckland has shown that opposing sides of the health fence can co-operate to cut sugar consumption.
The campaign involved McDonalds and Counties Manukau District Health Board in a pilot scheme to tackle high levels of type II diabetes. More than 12,000 people in the board's region have the disease and just as many may be undiagnosed.
Fast-food giant McDonalds agreed to the trial by serving only Sprite Zero to customers who asked for the drink. The non-sugar variant - it is sweetened, like all low or non-sugar brands with blend of low and no-kilojoule sweeteners - was not available before the trial started in December 2006. Results of the project outlined to a public health forum in Auckland found a mixed customer reaction, but a general perception of growing acceptance to the "Zero" bottle.
No one complained, but public awareness of the trial was low. Since the project, McDonalds has removed Sprite from all its New Zealand outlets, cut sugar in its buns, and added Coke Zero to its menu. The upshot was the removal of more than 300 tonnes of sugar from the company's food supply.
An evaluation of the project by an Auckland University health team concluded that "the health sector can influence industry", but added it needed "a lot of goodwill on both sides".