U.S. Obesity Prevalence: “Good News” or “Astounding” Surge?

When it comes to obesity, it seems everyone is looking for clickbait. Facts are incidental. So this week, we have wildly differing news headlines about U.S. obesity prevalence. The Harvard Gazette tells us we have an “astounding surge” in obesity prevalence. Axios tells us there’s “good news” on obesity prevalence.

Where does the truth lie? Deep in the details under the headlines.

The “Astounding Surge”

Of the two headlines, this was perhaps the most disconnected from the underlying study. In JAMA Network Open, Lindsay Fourman and colleagues examined the implications of the Lancet Commission proposal for creating separate definitions of preclinical and clinical obesity. They contrasted this with simply defining a BMI of 25-29 as overweight and a BMI of 30 and higher as obesity.

Broadly, they found two things. First, the number of people who fit the definition of either clinical or preclinical obesity was higher than the number who fit the simpler definition of BMI 30+. The sum of the two new categories was 69% prevalence. Prevalence under the BMI 30+ definition was 43%. This is where the clickbait headline of a “surge” originates.

But there’s no surge. In fact, there’s no analysis of trends over time – which is necessary for detecting a surge. A surge is an impressive increase in a given period of time. If one considers only clinical obesity to be important, then the prevalence is only 36% – a drop from the 43% number for BMI 30+.

There is in the study, however, plenty of interesting information in this analysis. For instance, they looked at the effects of the Lancet definitions of obesity on eligibility for treatment with obesity medicines. If one assumes that anyone with preclinical or clinical obesity has an indication for an obesity medicine, eligibility goes up. But if one assumes that only clinical obesity is an indication, then eligibility goes down.

This study is well worth a deep dive into its details.

The “Good News”

The source of the “good news” headline was the latest edition the State of Obesity Report from Trust for America’s Health. The finding here is that obesity rates remain high, but that fewer states have self-reported obesity prevalence of 35% or more.

Good news? Well, we take it with a grain of salt because these data come from self-reports of height and weight. People fudge the numbers. Everyone is slimmer and taller in their self-reports than the scales say. What’s more, many factors can influence the misreporting.

Based on everything we know, it might be that decades of rising obesity might be leveling out at a high level. Is the tide receding? We have doubts.

In all of this, a careful reader can find useful insights. We can do without the clickbait.

Click here for the new study in JAMA, here for the State of Obesity Report.

Brain Rot, still image from video by Singularidad Convergente, licensed under CC BY 3.0

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October 17, 2025