Why are so many Kiwis obese? DNA study to answer fat question

An increase in obesity rates in recent years has been put down to lifestyle factors. Photo / Getty Images

Our understanding of what causes obesity in Kiwis could change dramatically with a new million-dollar study drawing on the latest DNA technology.

Around one in three New Zealand adults are now obese - including nearly half of Maori and 68 per cent of Pacific Island people - and health researchers have labelled the rising rates a crisis.

But while an increase in obesity rates in recent years has been put down to lifestyle factors such as poor diet and a lack of exercise, the genetic predisposition to obesity, particularly among Maori and Pacific Island populations, has been less understood.

Now, a landmark study will use the latest genome-sequencing technology to analyse the DNA of more than 600 Kiwis, including a large group of adults considered at risk of obesity.

The work, to be led by the Auckland-based Maurice Wilkins Centre and being announced this morning at the Queenstown Research Week conference, will specifically target up to 500 genes suspected of affecting individuals' appetite and the way they control their energy metabolism.

The centre's deputy director, Professor Peter Shepherd of Auckland University, said there were long-standing prejudices around obesity, which many people unfairly dismissed as a result of laziness.

However, underlying genetic factors which especially put Maori and Pacific Island people at greater risk of cardiovascular diseases and type-2 diabetes were suspected to play a hidden role we were only just beginning to understand.

Learning more about these drivers could greatly improve how the health system tackled obesity, which was estimated to cost the country up to $850 million each year in health care costs and lost productivity.

Professor Shepherd suggested it could be possible to match patients' individual genetic profiles to targeted treatment, such as personalised diets.

"The study is a great step forward as it involves the best clinicians and scientists in this space from across the country putting their minds together to address this very important issue."

Helping to oversee the genetic analysis will be Associate Professor Tony Merriman of Otago University, whose work has rewritten what we know about gout in New Zealand, finding that 60 per cent of cases could be linked to genetic causes rather than just lifestyle factors.

"The technology to analyse genes is advancing rapidly and this type of study is now feasible in New Zealand," Professor Merriman said.

"Our experience in studying the genetics of gout suggests that the new study has a high chance of finding important new information that can be clinically useful."

Also involved is world-renowned Cambridge University obesity expert Dr Giles Yeo, who presents the new BBC documentary What Diet is Right For You, which attempts for the first time to match people's genetics with an appropriate diet to try to achieve better long-term weight loss.

Dr Yeo, who is in the country for the Queenstown conference, felt the new study would be important for New Zealand, while also contributing to global knowledge in the area.

"I believe there is a high likelihood this will lead to better strategies for achieving and maintaining weight loss in New Zealanders."

Obesity in NZ

•The 2012-13 New Zealand Health Survey found 31 per cent of adults were obese, while a further 34 per cent were overweight.

•A 2012 Auckland University study estimated obesity cost the country between $722 million and $849 million a year in health-care costs and lost productivity.

Professor Shepherd will discuss the issues on Thursday at a public lecture planned as part of the conference.