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Are Trends in Obesity and Overweight Shifting?

CDC and the National Center for Health Statistics have published new statistics on the prevalence of obesity and overweight. We already knew that obesity rates in 2016 were still rising. But with these additional statistics, we see signs of a subtle shift in trends.

Less Progression to Overweight

Since the 1980s, we’ve seen a rather constant trend of fewer and fewer people with a BMI in a healthy range. That is, with a BMI less than 25.

However, this most recent data suggests that trend might be reaching a limit – especially among men. The prevalence of BMI less than 25 reached 26.5 percent of men in 2006. And in the ten years since then, it’s pretty much stayed close to that. You can see this trend in the top graph on the right.

The same sort of slowing is not so apparent in numbers for women.

But Obesity Is Still Growing

However, you can see that the prevalence of obesity is still growing for both men and women. This means that more men are progressing from overweight to obesity. This is happening despite the fact that fewer people – especially men – are progressing from a healthy weight to a BMI of 25 or more.

Thus, the growth in obesity rates is coming more and more from people who already have some excess weight. And perhaps, we’re approaching a limit to the number of people in the U.S. population who are susceptible to the factors that are promoting weight gain. Are the people who still have a BMI less than 25 somehow resistant to those factors?

Forecasting an Equilibrium

This reminds us of a dynamic model of the obesity epidemic that Diana Thomas and colleagues published back in 2013. At the time, they wrote:

The US prevalence of obesity is stabilizing and will plateau, independent of current preventative strategies. This trend has important implications in accurately evaluating the impact of various anti‐obesity strategies aimed at reducing obesity prevalence.

So it may be that we are seeing the early stages of a plateau. Perhaps we are seeing that a quarter of the population is resistant to the same factors causing the rest of us to gain more and more weight over time. We can learn from these trends if we pay close attention.

Click here for the NCHS E-Stats report with the latest numbers for adults. For youth, you can find the numbers here. For our earlier post on dynamic modelling of the obesity epidemic, click here.

Lines, photograph © eLKayPics / flickr

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September 13, 2018

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