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The Wall Street Journal
written by Carl Bialik
Friday April 12, 2013
When Samoa Air made headlines with its announcement earlier this month that it would base passengers' airfares on their weight, many news articles noted that Samoa has one of the highest rates of obesity in the world.
The fact that Samoa and other Pacific island nations have taken their place atop the global obesity rankings shows how much has been learned in recent years about expanding waistlines world-wide: Only in the last decade have researchers been able to gather the data necessary to fully assess these relatively remote places.
But while the ranking by one widely used measure is accurate, it could also, many researchers say, be misleading: One size doesn't necessarily fit all when it comes to assessing the health risks from obesity.
Obesity for adults typically is defined as a body-mass index—the ratio of weight in kilograms to height in meters squared—of 30 or higher. But that definition "wasn't working quite as well for Polynesians," the predominant ethnic group in Samoa, said Wendy Snowdon, coordinator of the Pacific Research Centre for the Prevention of Obesity and Non-communicable Diseases at Fiji School of Medicine.
Dr. Snowdon and other researchers have correlated BMI with other risk factors for disease, such as body-fat percentage. They found that Polynesians with the same BMI as Melanesians—another ethnic group common in the Pacific—face lower risks of high blood sugar or high blood pressure. One possible reason: Polynesians typically have a higher proportion of body muscle. Other research has shown that New Zealanders of Indian origin have a higher body-fat percentage than New Zealanders of Polynesian origin with the same BMI. "It's an area of significant debate," Dr. Snowdon said.
"At a given body-mass index, a Polynesian will have more muscle mass than a Caucasian," said Colin Bell, the World Health Organization's technical officer for noncommunicable diseases in Suva, Fiji. The obesity rankings to some extent "ignore the differences in phenotype or physical body type."
Both Samoa's obesity ranking, and the finding that it may be overstated, have been made possible by a series of new health surveys in Samoa and its island-nation neighbors. The countries have become centers of obesity research, as their low populations—just under 200,000 in Samoa—mean that factors that have led to obesity elsewhere, such as widespread availability of processed food and sedentary lifestyles, took hold quickly, and that measures taken by the government to reverse the trend could also work fast
"It's a microcosm," said Maximilian de Courten, professor of global public health at the University of Copenhagen.
Begun in 2002, the surveys, prompted by and partially funded by the WHO, were intended to address concerns that some countries lacked any national obesity data, while others had numbers that weren't collected in an internationally standardized way.
The studies show that many Pacific islanders are now obese, by the WHO definition. The mean BMI for women 20 and older in Samoa in 2009 was 33.8, and for men, 30.5, after standardizing for the country's age distribution—each ranking fourth-highest in the world. Nauru, another Pacific island nation, ranked first, with 35.2 and 34, respectively.
Gathering height-and-weight data in countries spread over two or more islands, with many remote villages, is challenging. As a result, while the Steps surveys, as they are known, were meant to be conducted every five years, no country in the region has yet published results from a second one. The WHO's latest obesity estimates typically are extrapolated from now-dated surveys.
As the Samoa Air news broke, researchers in Samoa had just begun their second Steps survey, following up their first effort, in 2002, which studied nearly 3,000 adults. The results could show that even more Samoans have become obese, or that measures taken by the government have begun to reverse the trend.
What won't have changed are the definitions of overweight and obese. The cutoff for overweight, by WHO standards, is a BMI of 25, and 30 for obese. The research by Dr. Snowdon and others, though, suggests using thresholds of 27 and 32, respectively, for Samoans and the population of some neighboring countries would give a more realistic view of the risks they face of diabetes and other diseases associated with obesity, researchers say.
Shifting the obesity cutoff to 32 could make a big difference to prevalence figures, as many Samoans' BMIs are between 30 and 32, Dr. Bell said. But the WHO has kept standard cutoffs. "You really need that for global comparisons," he said.
Tuliau Sarah Faletoese Su'a, assistant chief executive for strategic planning, policy and research for Samoa's ministry of health, would like to see the definitions changed, calling it "hurtful" to be known for such high rates of obesity.
However, Temo Waqanivalu, coordinator of the WHO's South Pacific division for noncommunicable diseases and health promotion, who is sympathetic to the idea of shifting the cutoffs, said, "It's not just an issue of the wrong cutoff. Obesity in the Pacific is real."
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