The stages of an obesity epidemic

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February 5, 2019 —A new article by Lindsay Jaacks, assistant professor of global health at Harvard Chan School, and co-authors present for the first time a conceptual model of the so-called obesity transition, a model that could help policymakers identify strategies aimed at curbing rising obesity rates worldwide.

What are the four stages of the obesity transition?

The first stage is where a lot of countries in Latin America and the Middle East were in the 1970s. It’s the early stage where obesity is starting to be a major issue in terms of public health but not to the extent we are seeing today. Some of the characteristics of this stage are that obesity prevalence of a country is below 20% of the population; obesity rates are much higher in women than in men; obesity is more prevalent in people with higher socioeconomic status than in those with lower socioeconomic status; and obesity rates are much lower in kids than in adults.

The second stage is where a lot of Latin American and Middle Eastern countries are now. At this stage you see a big increase in absolute prevalence of obesity—prevalence could be as high as 35-40%, like we see in women in Mexico, Colombia, and Egypt. You’ll also see that rates of obesity are still higher in women than men, but the gap is closing. And rates of obesity in children are increasing.

The third stage is where the U.S. and many European countries are now. There is a really high prevalence of obesity, and, in a reversal, there’s now a higher prevalence among those with lower socioeconomic status than those with higher socioeconomic status.

The fourth stage is a hypothetical stage that we are hopeful will come to pass but, at this point, there’s not much evidence to support it. At this stage, the prevalence of obesity in a country declines. And we’ll probably see that decline first in children and women with higher socioeconomic status—there is some hint that this is occurring in the United Kingdom, for example.

Would it be possible for a country that’s in the first or second stage to leapfrog to stage four?  

 That would be an ideal scenario. If a country that’s in the first stage can implement strong policies around obesity prevention then we’d expect to see that country skip to the hypothetical stage four. The “soda tax” is certainly one of the most buzzed-about policies in this regard and has the most evidence supporting it. But it will require a multipronged effort with a significant focus on media campaigns and mobilization of civil society around health issues such as obesity and diabetes. One of the challenges is that when these types of policies have been implemented, they’ve been implemented in countries that are already far along in the transition and already have a high prevalence of obesity and people are dying from diabetes and its complications. Ideally you want countries that are in earlier stages implementing these strong policies to prevent them from ever getting to that point.

What are some of the challenges to countries that are considering enacting such policies?

Industry pushback is a major barrier and it’s similar to what the U.S. faced from tobacco companies when tighter laws were introduced to regulate the industry. Mexico experienced significant industry pushback when it was implementing its soda and junk food taxes back in 2013-2014. One of the ways it overcame this was by organizing policy makers, advocates, and stakeholders across different sectors, as well as the public, in the years leading up to the policies actually being enacted. Having that unified support was critical. And now we have pretty strong scientific evidence that there will be a decline in body mass index at the population level in Mexico over the next ten years. If that does come to pass, that will be the first-ever documented national decline in BMI ever recorded.

The study was published on January 28, 2019 in The Lancet Diabetes & Endocrinology

Chris Sweeney

Photo: Sarah Sholes