Canadian women are becoming overweight faster than almost any other women in the high-income world – and they’re putting that weight on as easily and quickly as Canadian men, a major new global analysis shows.
Worldwide, obesity has nearly doubled since 1980. More than half a billion adults were obese in 2008.
Three studies published in The Lancet this week tracking country-by-country trends for three major risk factors for heart disease over three decades show that while high-income western countries, including Canada, are lowering total cholesterol and blood-pressure levels, obesity is increasing in virtually every region of the world.
Overall, the world has been putting on weight at a rate of about 2 1/2 to three pounds a decade for each person on the planet. And Canada has some of the highest average body mass indexes among wealthy nations – still less than the United States, the heavyweight champion.
A BMI, or body mass index, is a ratio of weight to height. A BMI greater than 25 is considered overweight, according to the World Health Organization.
The Lancet papers estimated trends in 199 countries and territories. For the study on global BMIs, researchers obtained data from published and unpublished reports involving nine million people.
Among high-income countries, the U.S. had the single highest BMI (over 28 for men and women) in 2008, followed by New Zealand (over 27 for men and women). Japan had the lowest BMI (about 22 for women and 23 for men) followed by Singapore (about 24 for men and 23 for women).
The average BMI for Canadian women rose from 24.1 in 1980, to 26.7 in 2008. For Canadian men, the average BMI rose from 25.2 in 1980 to 27.5 in 2008.
In Germany, BMI rates for women increased from about 25 to 26 over the same 28-year-stretch.
Italy was the only high-income European country in which female BMI appeared to have actually fallen, albeit modestly, from 25.2 in 1980, to 24.8 in 2008.
Women in some western European countries, including Belgium, Finland, Switzerland and France had virtually no rise in BMI (less than one kilogram per metre squared) across the entire 28 years.
"No place has gone down in a meaningful way," said senior author Majid Ezzati, head of a global collaboration of researchers that includes Canadians.
"Some places it may be flat, but that’s definitely the exception."
Rigorous trials are needed to evaluate what’s working in the fight against fat – "and if it’s not working, abandon it," he said.
"If it’s taxing sugar-sweetened beverages, we should go after that. If it’s increasing bike lanes, we should be doing that."
One thing is clear, according to the researchers: simple advice and exercise alone aren’t working.
It will take decades to reverse the obesity epidemic, said Dr. Arya Sharma, scientific director of the Canadian Obesity Network and a professor of medicine at the University of Alberta.
"We need to get serious about thinking about treatment. We can all hope that prevention is eventually going to work, but it’s not going to work anytime soon and it certainly does not look like it’s working right now, because the numbers are continuing to rise," Sharma says.
"When you have a BMI of 26 as an average, that means that there’s a lot of people out there who actually have severe clinical obesity, and need treatment."
In 2008, nearly 1.5 billion adults were overweight, including 500 million who were obese, two McMaster University experts in population health wrote in an accompanying comment in the Lancet, the world’s leading general medical journal.
The results suggest that "(being) overweight affects one in three adults and obesity affects one in nine adults in the world – a tsunami of obesity that will eventually affect all regions of the world," doctors Sonia Anand and Salim Yusuf said.
The Lancet studies estimate that in 2008 there were also one billion people living with uncontrolled high blood pressure.
When all risk factor trends are taken together, "the forecast for cardiovascular disease burden in low-income and middle-income countries over the new few decades is dismal and comprises a population emergency that will cost tens of millions of preventable deaths, unless rapid and widespread actions are take by governments and health-care systems worldwide," the McMaster team said.
"The one encouraging thing is that, despite the increase in obesity, in high-income countries – but not all of them – we see a decline in systolic blood pressure and total cholesterol," Anand said in an interview. "We often consider, why is obesity bad? Because it increases other risk factors for things like heart disease and, in some cases, cancer, yet despite the increase (in BMI) we are able somehow to control the blood pressure and cholesterol."
From the authors’ analysis, it isn’t clear why. "But we think it’s due to better screening and better treatment," Anand said.
"While every high-income country is trying to figure out how do we control weight gain, at least we’re able to do something to prevent cardiovascular disease by affecting some of the other risk factors" driven by obesity, she added.
But Ezzati suggested we’re simply buying time.
"Lagging behind all of these things may well be a whole wave of diabetes coming," said Ezzati, chair in global environmental health at Imperial College London.
In addition to the diabetes risk, excess weight heightens the risk for heart attack, stroke and cancers and contributes to nearly three million deaths every year worldwide, the researchers wrote in The Lancet.
"Some have argued that increasing BMI is a pandemic that could reverse life-expectancy gains in high-income nations," they said.
High blood pressure is the leading risk factor for death from cardiovascular disease and causes more than seven million deaths every year worldwide. The analysis found that, in 2008, Canada, the U.S., South Korea and Cambodia had some of the lowest rates in systolic blood pressure – the pressure when the heart beats while pumping blood – for both men and women, below 120 mmHg for women and below 125 mmHg for men (the mmHg is millimetres of mercury).
Had people not been growing fatter since 1980, the drop in blood pressure would have been even more significant, the researchers note.
Scant data were available for cholesterol and blood pressure levels for low- and middle-income countries.
According to the studies, in 2008, nearly 10 per cent of men and 14 per cent of women in the world were obese.
Some Pacific Island nations have the highest average BMIs in the world, reaching 34 for men and 35 for women in Nauru.
The rare places in the world where BMIs were stable, or potentially even falling, were central and Eastern Europe for women, and central Africa and South Asia for men.
The researchers adjusted average BMI for age, to account for differences in the age composition of populations. For example, older people make up a larger proportion of European populations than African nations. Age-standardized estimates take these differences into account, otherwise it wouldn’t be possible to tell whether differences in BMI over time, or from one country to another were merely the result of older or younger populations.
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