For the first time in a decade, rates of adult obesity in the United States have dropped, a new study has found.

The study followed nearly 17 million people, the majority of whom were in the 26-75 age range, and found that after climbing steadily since 2013, rates of obesity in the U.S. fell 0.15% in 2023, according to a research letter published in the Journal of the American Medical Association (JAMA) on Dec. 13.

And while 0.15% might seem like a marginal drop, study author Benjamin Rader, scientific director at Boston Children's Hospital, told USA Today, "On the percentage level, the decrease appears quite small ... but when you actually look at the population, what that translates to is hundreds of thousands of people who were in an obese category and are no longer in that category."

"The population impact, we think, is quite big," he says.

The authors acknowledge that using Body Mass Index (BMI), a historically flawed way to measure obesity, is "imperfect" and "future studies should investigate alternative body composition measures and potential causes for the observed shifts, including GLP-1RA proliferation (eg, out-of-pocket purchases) or pandemic-associated demographic and behavior changes."

The most notable decrease in obesity was in the South, the study says, noting that that's the area with "the highest observed per capita GLP-1RA dispensing rate."

GLP-1A is a reference to semaglutide, which works in the brain to impact satiety. It's the active ingredient in Ozempic (prescription medication for type 2 diabetes) and Wegovy (prescription medication for clinical obesity). A recent study found that 6% of adults in the U.S. -- or 1 in 8 -- have taken the medication.

While the decrease is an "encouraging reversal," the study says "obesity remains a considerable public health concern."