But Martin's story is a rare one. The reality is, New Zealand is in the grip of an obesity epidemic that has gathered momentum in the past 30 years. A study in Lancet last week revealed that the proportion of obese adult males in New Zealand increased more than in any of the 188 countries surveyed, from 13 per cent to 28 per cent. Between 1980 and 2013, the proportion of overweight and obese adults jumped from 50 per cent to 66 per cent. Nearly one in three New Zealand children is obese or overweight. Three decades ago it was one in five.
Health economists can turn these trends into dollars. In terms of healthcare costs and lost productivity, the burden of an obese and overweight nation is between $722 million and $849 million a year, according to an NZIER report.
The cost of diabetes on the health budget is forecast by PriceWaterhouseCoopers to be an extra $1 billion every year until 2020.
The Government says it is investing strongly to slow the obesity cycle. Experts who work in the field say its policies, while commendable, are too limited to make a real dent in what has become a major public health crisis. They see the Lancet study, and its collection of shocking statistics, as a timely opportunity to alter what has become known as the "obesogenic" environment - the unhealthy mix of a diet of energy dense and nutrient-poor, relatively cheap processed foods and gradual lifestyle changes that lead to reduced physical activity.
Besides the $3 Zumba classes in Otahuhu, which attract regulars with Green Prescriptions - a Government-supported plan for GPs to "prescribe" physical activity for patients and families - millions in tax dollars are being poured into anti-obesity programmes.
Ten communities from the Far North to Invercargill are part of a four-year, $40 million "healthy families" plan, which copies a successful model used in Australia. Children in Victoria who took part ran longer, weighed less and had smaller waistlines than other youngsters.
More than $3 million has been invested in maternal and childhood nutrition, $2 million is available for stomach-stapling surgery on the public purse and nearly 90,000 children in 478 low-decile schools will get 18 million pieces of fruit this year to start the day on a healthy note.
But public health experts and scientists who study the drivers of obesity say current policy is nowhere near enough to turn the tide. They argue that the Government needs to tax unhealthy foods, insist on clear, front-of-pack food labelling, make significant investment in projects such as cycleways and back research that has found obesity can be an inheritable condition.
In other words, some individuals are genetically predisposed to eat without feeling satisfied, which means they find it hard to stop. They can have a defect which disrupts their "satiety mechanism", in the middle of a consumer-driven market where the cheapest food is often the least nutritious.
This is a new frontier in science, with limited understanding of how it might translate into health policy. Tony Merriman, University of Otago geneticist and co-author of the Lancet report, said genes helped explain why some people are obese and others not.
He says the ingrained view of the obese is that it's their fault because they eat too much - an outlook that found public expression in broadcaster Rachel Smalley's unguarded remarks about "lardos" and "heifers". (She later made a tearful, on-air apology.)
Dunedin biochemist Merriman says new research suggests that genes could explain as much as 70 per cent of individual weight differences - why only some people are obese.
The drive to eat can be influenced by stress and emotion - and by genetic variants. These variants can mean, for instance, that some individuals fail to get adequate signals that they feel full after a meal and help explain, says Merriman, why obese people find it that much harder to slim down to a normal body weight than the effort a lean person requires to stay trim.
He says science does not yet have the answers to all the biological drivers of obesity but it is clear that it is not a simple matter of people being unable to control their eating habits "which seems to be the view out there".
"I think we need to change this attitude towards obesity because it engenders a sense of social shame, a stigma, and is counterproductive."
Merriman says in the New Zealand context, the growing understanding about genes and obesity show the need for a research focus among Maori and Pacific communities, with the results being widely communicated.
The genetic link to obesity means drugs could be a weapon in weight loss policy, but Merriman says his position is that prevention is a preferable first step.
He thinks better understanding of the biological causes of obesity could nudge public opinion towards far greater support for new policies to attack obesity. A blueprint exists in measures used to reduce smoking, where years of taxes, law changes and public education campaigns drove home the links between cigarettes and disease.
At this point, however, it seems little is likely to change on the obesity front, at least on the Government policy front .
A spokeswoman for Health Minister Tony Ryall advised the Weekend Herald: "This Government does not support a fat tax or a sugar tax. The Government's preference is to provide information and support for individuals and families rather than nanny state regulation."
Public health specialists and obesity experts say that's fine as far as it goes but it's not enough, given that as many as 2.2 million New Zealanders need to lose weight. Why? Because being overweight is a risk factor for stroke, heart disease, cancer and dementia, four leading causes of death and disability in New Zealand. Overweight and obese people are more likely to have higher blood pressure, higher cholesterol and higher blood glucose - all the things that in turn cause higher coronary heart disease and stroke rates. Moreover, as the Lancet study showed, New Zealand has the highest rates of adult and child obesity in the region - a ticking time bomb for the health system and a serious economic burden.
Valery Feigin, a co-author of the Lancet report and director of the National Institute for Stroke and Applied Neurosciences at AUT, says two insights have emerged from the study. For a start, existing strategies for maintaining healthy weights are not working and secondly, urgent action is required by individuals and the Government.
Feigin advocates tax exemptions on fruit and vegetables, curbs on soft drink sales in schools and public places, and public awareness campaigns on good diets and healthy weights. He warns that if the obesity epidemic is not stopped, the country faces a growing cost.
University of Otago public health specialist Dr Nick Wilson argues for a novel move - spending on cycleways. Wilson, co-director of a project that studies the cost-effectiveness of interventions designed to relieve the burden of disease, said research from Portland, Oregon shows what can be done.
Cycling is popular in the northwest United States city, which encourages cyclists with bike-friendly streets and cycle-lanes. It has more than 500km of cycle tracks.
The payback, according to one study, has come in healthcare and fuel savings. Research shows that by 2040, Portland cycleway investments in the range of US$138 million ($162 million) to US$605 million will result in healthcare cost savings of US$388 million to US$594 million and fuel savings of US$143 million to US$218 million.
Even more striking, savings in value of statistical lives - a measure of the cost of a life - have been put at US$7 billion to US$12 billion.
Unlike Auckland, Portland is a flat city, which lends itself to cycling. But Wilson suggests that new-generation electric bikes could take some of the grunt out of the job of climbing hills in the city of sails.
He says the beauty of this initiative is that it could make headway on the exercise front, as people who regularly cycle or walk tend to consume less high-energy junk food.
"Building physical activity into the daily routine does help to regulate weight. In the last 20 years we've seen a big shift in children being driven to school and not cycling or walking.
"So if we made investments in safe cyclepaths or walkways and parents felt okay about kids using them, then we'd see the benefits."
Wilson also favours a 20 per cent sugar tax, a level he feels would be acceptable to politicians. By ring-fencing revenue earned from the tax so it could be spent on measures to improve diets and curb obesity, political and public support would rise dramatically.
"This is the evidence from tobacco tax increases globally. When the money goes to cancer research or quitting support, even many smokers support it."
He acknowledges the food industry would fiercely resist any food or sugar tax, "but when you see a country like France putting a tax on soft drinks, then it's time for us to seriously consider it".
The impact of soft drink taxes remains uncertain and the science is less than robust but Wilson argues it is worth investigating.
"Given the very strong evidence from tobacco and alcohol taxes - most public health academics suspect that a 20 per cent tax has a fairly good chance of a measurable impact in New Zealand."
Food and Grocery Council chief executive Katherine Rich rejects outright the call for a tax on sugar. She says it has been tried overseas in different forms and failed to do more than collect more money from citizens for Governments.
"In the last couple of years some have advocated for sugar taxes while others have called for fat taxes. Add them together and all you get is more expensive food at the supermarket."
She says tobacco taxes had cut rates of smoking because they were so high.
"Imagine what tobacco-style taxes would do to the price of food. Sugar taxes would seriously adversely affect those on low incomes and hit a lot of popular supermarket items such as jam and honey. Last year the University of Otago put jam and honey on a "Need not" list and received a lot of negative comments from the general public."
Equally Rich does not favour regulations imposing labelling rules on the food industry. The council has been involved with a new transtasman labelling scheme, which featured a star system. "We're sure it's on the right track."
University of Auckland obesity expert Dr Boyd Swinburn expects the food industry to steadfastly resist change. Swinburn, professor of population nutrition and global health, says the Lancet survey is proof that New Zealand has not done nearly enough to reduce childhood obesity.
He believes the present Government is on the right track with its Healthy Families programme, but has shied away from serious policy interventions that all expert groups recommend - "things like reducing junk food marketing to kids, taxes on junk food, labelling on the front of packages that people can understand and against which there is substantial industrial opposition".
He adds: "This Government has purposely not gone down that track. I'm afraid the current approach of not taking those steps means we get more and more obesity."
But there is at least one hopeful sign, at least for children.
Early next year, the World Health Organisation will outline measures to "end childhood obesity". Sir Peter Gluckman, the Prime Minister's chief science adviser, is a joint chairman of the commission given the task of designing the plan. The commission includes two other high-profile New Zealand figures - former Prime Minister Helen Clark and Dr Colin Tukuitonga, who heads the SPC, the regional Pacific commission. He is a former head of the Ministry of Pacific Island Affairs.
Two working groups have been set up, one to look at all available evidence on prevention of childhood obesity and how to reverse it in affected children. The other group will determine how to monitor gains in tackling childhood obesity worldwide and track results.
The childhood focus has resonance for New Zealand, given the Lancet finding that 29 per cent of children here are either overweight or obese. Such children are at higher risk of asthma, cognitive impairment, diabetes, heart disease, some cancers, respiratory diseases, mental diseases and reproductive disorders later in life. They face hurdles joining in play, can suffer at school and become a burden on their family.
Obese children often remain that way in adult life. But equally, children are far more responsive than adults to interventions that provide healthier food and environments of physical activity - so it makes sense to intervene as early as possible.
Swinburn believes the presence of three influential figures with strong New Zealand connections could give the WHO report some horsepower in this country.
He says it is time for New Zealand to "be a leader rather than a laggard in obesity prevention. It's time we gave kids a little bit of protection of their health rather than looking after the junk food industry's wealth."
