乡村生活方式会让人更胖吗？| Nature Podcast
又到了每周一次的 Nature Podcast 时间了！欢迎收听本周由 Nick Howe 和 Benjamin Thompson 带来的一周科学故事，本期播客片段讨论乡村生活方式与肥胖。欢迎前往iTunes或你喜欢的其他播客平台下载完整版，随时随地收听一周科研新鲜事。
音频文本：
Interviewer: Benjamin Thompson
Around the world, people’s waistbands are getting bigger. Back in 2016, the WHO estimated that globally, over 1.9 billion adults were overweight and over 650 million of them were obese. But what’s causing this epidemic? Well, new research suggests that a prevalent theory of what’s going on might not be giving the full picture. So, what is this theory? Here’s Majid Ezzati from Imperial College London to explain.
Interviewee: Majid Ezzati
The belief out there is that living in cities actually is the main driver of the obesity epidemic. In some sense, actually, the broad paradigm is that as people move to cities, they consume worse foods, they become less active and hence they become obese.
Interviewer: Benjamin Thompson
If this is correct, there may be significant impacts on future obesity levels, as the United Nations suggest that 68% of the of the world’s population could be city dwellers by 2050.
Interviewee: Majid Ezzati
People believe that we eat more processed and more fast foods if we live in cities. People believe that we use less energy, we are physically less active because living in cities is associated with certain patterns of travel and work.
Interviewer: Benjamin Thompson
So, if that’s the presumed city experience, what’s it like for people living in the country?
Interviewee: Majid Ezzati
In some sense, there has been a romantic view of living in rural areas which is that people eat fresh, healthy foods and are going about their work in active ways, so it has been this extreme, assumed contrast of rural and urban life.
Interviewer: Benjamin Thompson
So, the prevailing view is that urban lifestyles are a big reason for the increase in obesity rates around the world, but is this correct? Perhaps not, according to research that Majid and his colleagues have published in Nature this week. They’ve been looking at the body mass index – or BMI – of rural and urban populations around the world, and how they’ve changed over time. Now, BMI is calculated by dividing an adult's weight in kilograms by the square of their height in metres. The value gives an idea of whether that person’s weight is healthy or whether they might be underweight or overweight. Majid and his colleagues pulled together a lot of data from studies done all over the world between 1985 and 2017.
Interviewee: Majid Ezzati
We had over 2,000 studies. Among them, these studies, they had measures of height and weight of well over 100 million people going back to 1985. So, a lot of measurements.
Interviewer: Benjamin Thompson
By combining data on people’s BMI and whether they lived in a rural or urban setting, the team could build up a picture of how average BMI was changing in individual countries and regions over time. What they found was that although BMIs were increasing everywhere, it wasn’t just down to people living in urban settings.
Interviewee: Majid Ezzati
The majority of the rise in body mass index, in BMI, in the world has actually been due to the rise in rural areas. At the most basic level, the paradigm that we have currently – when we look at all of the data in the world – is actually incorrect.
Interviewer: Benjamin Thompson
In fact, the team suggest that more than 55% of the rise in BMI across the globe was due to increases in rural areas. In some low- and middle-income regions, this figure was as high as 80%.
Interviewee: Majid Ezzati
So, the really interesting thing is actually what’s been happening in middle-income countries. So, these are places like Latin America, parts of the Middle East, north Africa, parts of southeast Asia. In these places, actually, BMI has been going up noticeably faster in rural areas than in urban areas, and a bit more so for women than for men. So, you come to countries like Chile, that in the 1980s there was, if you wish, an urban excess or a rural deficit in BMI, and over time, they have actually reversed. There is now actually higher BMI in rural areas than there is in urban areas.
Interviewer: Benjamin Thompson
This finding – that BMI rates were increasing at the same rate or faster in rural populations – was also seen in those living in low-income countries, with the exception of women in sub-Saharan Africa for whom BMI rose faster in cities than in rural areas. So, what’s going on? Majid thinks that changes to the rural landscape in many regions is playing an important role. He suggests that while improvements to transport infrastructure and an increase in levels of mechanised agriculture are bringing economic and health benefits, they could also mean that people are able to consume more calories and expend less energy, resulting in a BMI increase. Majid also suggests that contrary to the view that urban environments are intrinsically unhealthy, they might actually offer some advantages – giving higher access to healthy foods like fruits and vegetables all year round, for example. Taken together, the results of this new paper rather turn on its head the view that city living is the main reason for the global increase in BMI. Barry Popkin from the University of North Carolina at Chapel Hill, who has written a News and Views article on the new research, thinks the way the team went about analysing the millions of measurements adds weight to their findings.
Interviewee: Barry Popkin
Their methods are solid. They took data that they’ve worked on and developed over a long period of time. They took a lot of national surveys, but when they didn’t have national surveys, they took smaller surveys and extrapolated them and worked on them with very sophisticated statistical methods to kind of replicate national populations. It’s based on a lot of years of work that this team has done they they’ve pulled together into this study.
Interviewer: Benjamin Thompson
Barry thinks that the results of this study will mean that policymakers will have to adjust their efforts when it comes to tackling problems like obesity. He suggests they will need to develop interventions that consider the issues facing people in rural areas.
Interviewee: Barry Popkin
This is going to be country by country. This means countries have to realise that rural areas face the same problems and start to think of either national solutions or think about a special programme for rural areas. Ways to improve activity will help, but it’s really in the food system. They have to find ways to get rural people to start to eat healthier in the same way we need to do it in urban areas.
Interviewer: Benjamin Thompson
That was Barry Popkin. Head over to nature.com where you’ll find his News and Views article, along with Majid Ezzati’s paper.
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