It is not surprising to see the media reach for the sensationalist headlines when a new study about “obesity” comes out. Today’s headlines were all on the same theme – the “Tsunami of Obesity” that is sweeping the planet. It’s an interesting use of a word which I don’t normally associate with “obesity”. So I wondered why researchers were suggesting that there was such a “Tsunami” and what evidence there was to back up this claim. Thanks to a couple of wonderful sources I managed to get a hold of the research papers related to the media frenzy, and this is my take.
The “Global Burden of Metabolic Risk Factors of Chronic Diseases Collaborating Group” released three reports today that describe global population-level changes in body-mass index (BMI), systolic blood pressure, and cholesterol over three decades. I’ll be frank: I have not read through the articles relating to blood pressure and cholesterol. Each article covers its own subject area and was then summarised in a further commentary. My review considers the research undertaken in regards to the BMI and the summary of all three reports.
The report notes that in 2008, 1.46 billion adults had a BMI of over 25, with 502 million of those with a BMI of over 30. The summary indicates that this means that “obesity” affects one in nine adults. I’m not sure that one in nine constitues a tsunami. The report also shows that the prevalence of “obesity” is nearly twice that which existed in 1980.
All of these figures sound really scary when you leave them on their own like that. There is no context. So let’s add some context.
Over the study period (1980 to 2008) the mean global BMI increased by 0.4-0.5 per decade, which is roughly 1.12-1.4. The mean BMI for women was higher at 24.1 whilst mean BMI for men was 23.8. It should be noted that men had a higher BMI than women in high-income regions, while this trend reversed in medium- and low-income regions. It’s important to note that the largest mean BMI values for both men (33.9) and women (35.0) came from Nauru. The lowest values were found in east Asia and high-income Asia-Pacific sub-regions (21.4-2.9) for women and in sub-Saharan Africa and in east. south and southeast Asia (20.6-28.1).
In the discussion, the paper looks deeper into these figures. There are two important parts that I think need to be considered by the media and the world at large:
Research is undoubtedly needed into the proximal and distal causes of the recorded trends. For example, to what extent have changes in physical activity versus increases in caloric intake or changes in dietary composition brought about BMI rise? What explains the heterogeneous BMI levels and trends, including by sex, in high income countries (Asia-Pacific vs western Europe vs Australasia and North America) or in Africa’s sub-regions?
Or in other words, why are BMI trends and levels not similar within countries with similar socio-economic levels or even in similar regions of the world? Some high-income countries to have low increases in BMI, for example France and Switzerland yet other countries with a similar socio-economic level such as Australia had larger increases.
They further point out how more research is required into the efficacy of long term weight loss benefits:
Randomised studies of diet change, some of which increase the amount of exercise, have shown moderate weight loss benefits for up to 2 years, but long-term and community effectiveness of such interventions is not clear. Simple advise and exercise alone have not been efficacious, even in trials. Structural, regulatory and economic interventions have potential to change physical activity of dietary patterns for whole communities and populations, but few have shown effects on weight.
There goes a few of the weight loss industry myths right there. But they go further:
That interventions on metabolic mediators might partially mitigate the health effects of rising BMI is supported by results from randomised trials, and more importantly from the fact that many countries have successfully reduced blood pressure and lipids despite rising BMI, and by a larger amount in people with high BMI.
So dispite the “Tsunami of obesity” research supports the fact that increasing metabolic rates through exercise can mitigate the health effects of being fat. I take that to read that you can be fit and fat. I’m not a scientist, but that’s what I read. How about you?
As a final note, it should be noted that the research into BMI did not mention the term “Tsunami”. This was part of an overall commentary of the three pieces of research. In fact, the title of the commentary was “Stemming the global tsunami of cardiovascular disease” (my emphasis). They did mention a “Tsunami of Obesity” in passing but the main comment they are passing is that urgent attention needs to be paid to cardiovascular health. So I wonder why the media decided to focus on the “Tsunami of Obesity” instead of the “Tsunami of Cardiovascular Disease”?
National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9·1 million participants
Mariel M Finucane AB,Gretchen A Stevens DSc,Melanie J Cowan MPH,Goodarz Danaei MD,John K Lin AB,Christopher J Paciorek PhD,Gitanjali M Singh PhD,Hialy R Gutierrez BS,Yuan Lu MSc,Adil N Bahalim MEng,Farshad Farzadfar MD,Leanne M Riley MSc,Prof Majid Ezzati PhD,on behalf of the Global Burden of Metabolic Risk Factors of Chronic Diseases Collaborating Group (Body Mass Index)
The Lancet – 4 February 2011
Stemming the global tsunami of cardiovascular disease
Sonia S Anand,Salim Yusuf
The Lancet – 4 February 2011