Obesity dipped slightly in U.S. adults last year, research found — the first time in more than a decade that the country has seen a downward trend. That might be due, in part, to the recent rise of blockbuster weight loss drugs like Ozempic, according to the study authors. 

The findings, published Friday in the journal JAMA Health Forum, showed the most significant decrease in the South, particularly among women and adults ages 66 to 75.

The study looked at body mass indexmeasurements of more than 16.7 million adults across different geographic regions, age groups, sexes, races and ethnicities from 2013 through 2023. BMI measurements, which are a standard but limited way to estimate obesity as a ratio of weight to height, were gathered from electronic health records.

The researchers found that the prevalence of adult obesity in the U.S. decreased from 46% in 2022 to 45.6% in 2023. (Those are slightly higher shares than the estimate from the Centers for Disease Control and Prevention, which says around 40% of U.S. adults had obesity from 2021 to 2023.)

The results were not uniform across demographics and geographic regions, said Benjamin Rader, a computational epidemiologist at Boston Children’s Hospital and an author of the study.

“In the U.S overall, obesity was on the decline, led by the South, but in some regions that wasn’t the case,” he said. “We also saw large drops among Black Americans, but we saw increases in obesity among Asian Americans.”

Rader said the decline in the South is notable because that region also had the highest observed per-capita uptake of weight loss drugs, based on the researchers’ analysis of insurance claims. But he acknowledged that any possible connection there needs further investigation.

The study authors also noted that the South experienced a disproportionately high number of Covid-19 deaths among people with obesity, which could have affected the overall data.

Dr. Michael Weintraub, an endocrinologist and clinical assistant professor at the New York University Grossman School of Medicine, said the results were in line with recent data from the CDCthat showed a slight downtick in obesity prevalence among adults in the U.S. in the 2021-2023 period, as compared with the years from 2017 to 2020 (though severe obesity rose over that time).

“I find the data exciting, and with the prospect that we could be at the precipice of a shift in this obesity epidemic,” said Weintraub, who was not involved in the new study. “But I hesitate to call this down-trending value in 2023 yet a trend.”