Tonga's eccentric king, who died on Sunday, was known to the world for his London taxi, his military uniforms and his hats.

But alongside the democratic reforms he introduced during his reign, King George Tupou V may be remembered for another legacy - his support for better understanding and treatment of the diabetes that afflicted him and many of his people.

The 63-year-old king, who died in intensive care in a Hong Kong hospital, had previously been treated for cancer. He also had type 2 diabetes.

He took a keen interest in diabetes research and in 2008 established the Royal Endocrinology Society, a charity to provide treatment, undertake research and promote prevention.


The king understood the threat posed to Pacific peoples by diabetes.

"If not properly managed," he said, "it can completely and painfully break the health, and lead to the death of its victims. It hurts their families, puts strain on already overstretched medical services, and has a negative economic impact."

Pacific nations - and Pacific peoples in New Zealand - have high rates of type 2 diabetes, underpinned by the world's highest rates of obesity, a big risk factor for the disease.

Type 2 diabetes means the pancreas produces too little insulin, or none at all, and the body can be resistant to the hormone. Insulin is needed to process glucose for energy and storage. Poorly controlled diabetes can result in blindness, kidney failure and amputations.

In New Zealand it's estimated just over 200,000 people - 5 per cent of the population - have diabetes, including around 15,000 who have the type 1 disease, an auto-immune disorder whose cause is unknown.

The diabetes rate for Pacific Islanders is 10 per cent - twice the national rate - while for Asians it is 6.5 per cent, Maori 5.8 per cent and for Europeans/others, 4.3 per cent.

The national rate is growing faster than the population - partly because of increasing obesity and the increasing proportion of older people (type 2 diabetes is mainly a disease of the middle-aged and elderly).

As well as being ethnically skewed, the prevalence of type 2 diabetes - and obesity - varies by socio-economic class: poor suburbs have twice the rate of wealthy ones.

Most health districts have a fairly uniform level of diabetes, except South Auckland, where the Counties Manukau District Health Board reports a rate of 8.2 per cent. This is driven particularly by the area's high Pacific population (22 per cent).

Indians almost stand with Pacific Islanders in South Auckland as having the highest rates of diabetes, but in actual numbers, Pacific Islanders are the largest ethnic group with the disorder at nearly 10,000.

Obesity is a global problem, but it's worst in Pacific nations. More than 75 per cent are overweight or obese in Tonga, Samoa and the Cook Islands. In New Zealand, the Pacific overweight/obese rate is even higher, at 88 per cent.

"The rapid rise in unhealthy weight gain among the New Zealand Pacific population occurs at a very early age, approximately 50 per cent of 5 to 6-year-old children already being overweight or obese," say Associate Professor Robert Scragg, of Auckland University, and his international colleagues in a series of reports on their major research attempt to prevent Pacific obesity.

"New Zealand Pacific children appear to have one of the highest prevalence levels of overweight and obesity in the world."

Around 30 per cent of NZ Pacific adolescents are obese and a further 40 per cent or so are overweight.

Dr Brandon Orr-Walker, clinical director for diabetes at the Health Ministry and head of endocrinology at South Auckland's Middlemore Hospital, said some ethnic groups, including Maori and Pacific peoples, were genetically more susceptible to type 2 diabetes than others.

This was reinforced by the cultural importance of giving and receiving food, and the widespread association between lower incomes and consumption of high-fat, high-energy foods. Obesity greatly increased the risk of developing type 2 diabetes.

"If your genetic predisposition is that you're more likely to develop diabetes, and if you're going to have an increased risk as you age, which is true for all of us, then obesity is the preventable factor in the equation."

The Pacific obesity prevention research - which ran in New Zealand, Victoria, Tonga and Fiji - tested interventions in four high schools in Mangere, a majority Pacific area.

"We were unsuccessful in showing an effect in Auckland," said Scragg. "Our Victorian colleagues were successful.

"The main conclusion was that to tackle obesity, you can't rely on people to do it by making individual choices. We must try and change the environment to make it less obesogenic."

However Auckland University of Technology's Project Energize, which provided healthy eating and physical activity programmes in Waikato schools, succeeded in reducing the proportion of primary age children who were obese or overweight.

Many public health experts link the rapid rise in obesity to the "environment" - being driven to school, and the easy availability at or near schools of pies, hot chips, sugary drinks and other cheap, energy-packed items. They want taxes on sugar, salt and unhealthy fats, tax relief on fruit and vegetables, and a ban on advertising junk food to children, including on websites.

Many lament the National Government's reversal of Labour's rule restricting the sale of unhealthy foods at schools.

The multi-university study revealed that teenage Tongan boys wanted to develop a strong, muscular body, especially for rugby success. Those growing up in Tonga were more attached to the "large body ideal" than those in New Zealand.

Teenage Tongan girls were more likely than some other groups to try to increase weight and muscle and wanted a large but healthy body.

Paul Lavulo, of the Langimalie Tongan Health Clinic in Auckland, said Tongans wanted to be large and strong, "but not obese and flabby".

"Diabetes is becoming an issue for the Tongan community ... There's more concern now by parents to teach their kids to eat more healthily and limit intake of food."

The clinic's Pacific nutritionist works with churches to develop healthy eating habits.

At Mangere College, school nurse Mary Dear has helped put in a school and community garden. On Wednesday afternoons, about 20 students work in the organic fruit and vegetable garden with an expert from the Diabetes Project Trust. Dear gives them a healthy snack and also has the Heart Foundation run healthy eating and cooking sessions at the school.

Year 11 student Sonny Tutagalevao loves the garden and has transferred his skills to his home garden. "We learn things and grow new plants. It's about having fun in the garden."