The Long Arc of Obesity Prevalence

The question that fuels much curiosity about obesity seems simple enough. What is it that sparked an increase in the prevalence of obesity beginning in the 1980s? But a new paper in Science Advances suggests this may altogether be the wrong question. That’s because Mads Møller Pedersen, Claus Thorn Ekstrøm, and Thorkild I.A. Sørensen have data to say the origins of the long upward arc of obesity prevalence came decades earlier. They tell us:

“Our findings indicate that the processes that induced the epidemic likely have been active much earlier and have grown steadily, affecting primarily the individuals with BMI in the upper quartile of the distribution and more so the further up in percentiles.

“It may be necessary to ask what caused the much earlier percentile changes to identify the roots of the obesity epidemic.”

First Showing Up in Very High BMI Ranges

Pedersen, Ekstrøm, and Sørensen paid close attention to the uppermost percentiles of BMI in persons born from 1939 through 1959. These data come from Danish school children and young military conscripts. In all they had data on more than half a million individuals.

In this time frame, the BMI of persons in the 50th percentile was relatively constant for successive birth cohorts. But for the 99th percentile – the heaviest one percent of the population – average BMI rose clearly for successive birth cohorts. In short, the growth in obesity began many decades before many people presume it did. The increases started with people who were most susceptible – those in the top percentile of weight for height. It didn’t show up in most of the population until much later.

Looking for a Spark in the Wrong Time

This adds to reasons we may not find a single elegant model to explain what sparked the enduring rise in obesity. Its origins go back much further than most people imagine. Very likely, there have been many sparks to fuel the blazing increases we have seen so clearly in recent years.

Click here for this fascinating new paper. For a thorough discussion of causes for the challenges we face with obesity, we recommend a two-part issue on this subject from the Royal Society, here and here.

Energy Arc, photograph by PiccoloNamek, licensed under CC BY-SA 3.0

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September 16, 2023