US obesity rates drop for 1st time in a decade, with possible help from weight loss medications

For the first time in over a decade, obesity rates in the United States may finally be heading in the right direction and new weight loss drugs like semaglutide could be part of the reason why.

A new study published Friday in the journal, JAMA Health Forum, found that obesity numbers ticked down slightly from 46% in 2022 to 45.6% in 2023. While only a slight decline, this is the first drop recorded in at least a decade.

"What we're seeing for the first time is that curve is bending and shows a sign of hope for something that was really a threat to American public health for so many years," said study co-author and ABC News contributor John Brownstein, who is also the chief innovation officer at Boston Children's Hospital and a professor at Harvard Medical School.

The study reviewed the body mass index (BMIs), a measure of obesity, of 16.7 million U.S. adults over a 10-year period. The average BMI rose annually to 30.24 -- which is considered obese -- until it plateaued in 2022, then dropped marginally to 30.21 in 2023.

Brownstein and his team noted that women and adults aged 66 to 75 saw the largest decreases in obesity. People living in the South, where they had the highest dispensing rate of weight loss drugs known as GLP-1 receptor agonists, also saw a meaningful decline in obesity.

Semaglutide, which belong to a class of drugs known as GLP-1 agonists, is the active ingredient found in the popular weight loss drugs Ozempic and Wegovy. The U.S. saw a 700% increase in the use of these drugs specifically for weight loss, from 2019 to 2023, according to one Annals of Internal Medicine study. They are also used to treat type 2 diabetes or a combination of diabetes and obesity.

Brownstein said that the growing use of these medications may be helping to reverse obesity trends.

However, there could be other factors at play, he added.

For example, while data looking at pharmacy prescriptions showed that the South had the highest dispensing rate of weight loss medications, this area also experienced a disproportionately high number of COVID-19 deaths among people with obesity.

Lifestyle changes as people emerged from pandemic isolation could also be playing a role, the authors suggested.

"You have this emergence from COVID, of which people are potentially starting to be more active again, stopping the sedentary habits that they picked up during COVID," said the paper's co-author Benjamin Rader, who is an assistant professor at Harvard Medical School. "All of these forces are at play, and I don't think we can disentangle them from this data."

And, while the findings are encouraging, experts caution that it's too soon to tell if this trend towards shrinking waistlines will continue.

"I think we need to look at this as a positive indicator in a specific database. That may mean that people are doing better and that including therapies are helpful, but we need to see how that plays out over time," Anne Peters, MD, a professor at the Keck School of Medicine, told ABC News.

Obesity remains a critical public health issue.

Nearly 60% of U.S. adults with obesity have high blood pressure and approximately 23% have diabetes, according to the Centers for Disease Control and Prevention. People with obesity are also at higher risk for heart disease, liver disease, and a long list of other chronic health conditions.

But Peters pointed out that BMI is just one measure of overall health. A person's weight should be considered alongside other risk factors to get a full picture of an individual's overall health and risk of chronic disease.

"You've got to combine weight loss with exercise and a healthier diet," Peters recommended. "I think we need to change how people eat fundamentally and that would be much better than people just losing weight."

Niki Iranpour, MD is an internal medicine resident at NewYork-Presbyterian/Weill Cornell Medical Center and a member of the ABC News Medical Unit