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Clocktower clockThursday 29 May 2014 8:25pm


Half of New Zealand's overweight women are obese and nearly a third of boys and girls are overweight or obese, according to a first-of-its-kind global report of which a University of Otago scientist is a co-author.

The report found that rates of being either overweight or obese have climbed among New Zealanders since 1980, according to a new analysis of trend data from 188 countries. The adult overweight and obesity rate in the country is 66%, up from 50% during the past 33 years. Among children in New Zealand, 29% are either obese or overweight, up from 18% in just over three decades.

Published in The Lancet on May 29, the study, “Global, regional, and national prevalence of overweight and obesity in children and adults during 1980–2013: a systematic analysis for the Global Burden of Disease Study 2013,” was conducted by an international consortium of researchers led by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington.

Associate Professor Tony Merriman of Otago's Department of Biochemistry was a member of the study consortium.

Overweight is defined as having a Body Mass Index (BMI), or weight-to-height ratio, greater than or equal to 25 and lower than 30, while obesity is defined as having a BMI equal to or greater than 30.

An estimated 2.2 million adults in New Zealand are overweight, and of these, 960,000 are obese. Of the country's men, 450,000 are obese and 510,000 women are obese. Within the Australasia region, (Australia and New Zealand) New Zealand has the highest rate of obesity in both adults (29%) and children (9%).

Half of all overweight women in New Zealand are obese. Obesity rates for women age 20 or older reached 30%, more than triple the obesity rates among girls (9%). Among boys, obesity climbed from about 10% in childhood and adolescence to almost 28% in adulthood.

By age group, there are four different ranges with the greatest proportion of overweight or obese men—all at 79%: age 50 to 54, 60 to 64, 65 to 69, and 70 to 74. Women aged 65 to 69 are the most obese at 73%, but women aged 70 to 74 and 60 to 64 rank second, both at 71%.

Boys 10 to 14 are the most overweight or obese at 33% and the same is true for girls also 10 to 14 at 31%.

When looking at obesity alone, Australasia experienced the largest absolute increase in adult obesity since 1980 (from 16% to 29%) and the single largest increase in adult female obesity (from 17% to 30%) globally.

Associate Professor Merriman says that it is widely accepted that increased calorific intake from energy dense and nutrient poor processed foods is a major driver of the increasing obesity rates in New Zealand and world-wide.

“Decreasing levels of physical activity owing to society-wide changes in lifestyle in adults and children also contribute.

“In my opinion the intervention required to reverse the increasing obesity rates is not straightforward and certainly will be multifactorial, requiring strategic co-ordination by government.

“It has to begin with public health approaches to reduce the total calorific intake of New Zealanders alongside approaches to increase physical activity. The former would require governmental policy change and specific interventions, such as reducing the price disparity between nutritious healthy foods and energy dense nutrition-poor unhealthy food.”

He notes that the food industry would also need to be engaged in this.

“This is generally a politically unpopular approach and would need to be coincidental with increasing public education and awareness of the biological causes of obesity. Increasing physical activity would be need to be multi-sectorial — local and central government, workplaces, schools.

“Alongside the approaches above it is my opinion that research efforts in New Zealand should be stepped up to focus on the biological drivers of obesity, particularly in Maori and Pacific people, with strong public dissemination strategies,” Associate Professor Merriman says.

He says that the National Science Challenges should be able to address this question.

“This research is required in order to change ingrained societal attitudes to the obese. Obesity is widely perceived to be the fault of the individual, who lacks the will to be lean. Contrary to this view, however, overseas research has shown that obesity is a heritable neurobehavioral condition sensitive to environmental conditions.”

Associate Professor Merriman says the 'obesogenic' environment increases the average weight, but genes are a major part of the explanation as to why some people are obese and others aren't, explaining 60-70% of the inter-individual variation in weight.

“These genetic variants, because they are inherited at conception, define biological causes of obesity. Many of these genetic variants have been identified - they highlight inadequate satiety signals and energy balance as important biological drivers of obesity.

People who have inherited a greater proportion of obesity-predisposing genetic variants need to exercise more conscious effort to remain lean in an obesogenic environment (i.e. to feel hungry in the presence of abundant food) than that required by a naturally lean person, he says.

“Wider public understanding of these biological causes should swing the public opinion pendulum on obesity from antipathy to sympathy, necessary for any successful governmental and other interventions to address obesity.”

A list of Otago experts available for media comment is available elsewhere on this website.

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