Adolescents who undergo bariatric surgery face a higher risk of weight regain, which can undermine treatment success and long-term health, if they have elevated blood levels of per- and polyfluoroalkyl substances (PFAS) prior to the procedure, according to new USC research.

PFAS are manufactured chemicals used in consumer products that accumulate in the body over time and are increasingly linked to a range of health concerns, including kidney problems, liver damage and various cancers.

The findings are published in the journal Obesity.

Bariatric surgery, a form of weight-loss surgery that alters the digestive system, is an effective treatment for severe obesity that can reduce the risk of long-term health problems such as type 2 diabetes and cardiovascular disease. But many people who get bariatric surgery regain significant weight over time, which can limit the procedure’s long-term health benefits.

Researchers believe PFAS exposure may play a role in weight regain because the chemicals are known to disrupt endocrine and metabolic processes.

“With the growing use of weight loss interventions around the world, it’s critical for us to understand the association between PFAS and successful weight loss management, including what this means for long-term outcomes,” said Brittney Baumert, Ph.D., MPH, a postdoctoral research fellow in population and public health sciences at the Keck School of Medicine of USC and the study’s first author.

Baumert and her colleagues conducted the first long-term study linking PFAS exposure to bariatric surgery outcomes in teens. They tracked 186 adolescents for five years, finding that those with higher PFAS blood levels before surgery regained more weight and had greater increases in waist circumference than those with lower PFAS levels.

The strongest associations were observed in a class of PFAS known as sulfonic acids, which includes perfluorooctanesulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS) and perfluoroheptanesulfonic acid (PFHpS).

The findings could help health care providers tailor treatment plans to better serve patients, as well as offer hints about the biological mechanisms that underlie the health effects of PFAS. The study also underscores the need for stronger limits on PFAS levels in food packaging, water supplies and other sources of exposure, the researchers said.

“Our study shows a clear association between PFAS exposure and weight-related outcomes in bariatric surgery for adolescents,” Baumert said.

“PFAS are a modifiable risk, which is why protective policies are so important to reduce exposure and safeguard public health—especially for vulnerable populations.”

Tracking long-term outcomes

The researchers analyzed data on 186 teens from the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study who underwent bariatric surgery between 2007 and 2012.

Before surgery, blood samples were collected from each patient and tested for levels of seven types of PFAS. Weight, body mass index (BMI) and waist circumference were measured before surgery and six months, one year, three years and five years after surgery.

To analyze the data, the researchers divided patients into three groups based on their blood PFAS concentrations: low, medium and high exposure.

Overall, patients with higher blood levels of PFOS, PFHxS and PFHpS gained more weight and had greater increases in waist circumference one to five years post-surgery, compared to patients with lower blood levels of those chemicals.

To illustrate the difference for PFOS, adolescents with a starting body weight of 328 pounds in the low exposure group regained, on average, 35.9 pounds by the five-year mark. But teens of the same weight with the highest PFOS exposure regained, on average, 46.9 pounds.

For PFHpS, teens in the highest exposure group regained weight at an average of 4.3% of their baseline bodyweight per year, compared to 2.7% per year in the lowest exposure group.

Better patient care

The study adds to the mounting evidence supporting stronger regulation of PFAS, the researchers said—particularly in public water supplies, which are the greatest source of exposure.

It also points to potential strategies for improving patient care. Bariatric surgery is costly and invasive, so understanding who is likely to benefit can help providers make informed decisions about the best course of treatment for each individual.

“We’re also interested in exploring whether PFAS exposure is relevant to other weight loss interventions,” including GLP-1 medications such as Ozempic, Baumert said.

In addition, Baumert and her team are investigating the link between PFAS and long-term metabolic health. For example: how might PFAS exposure relate to a person’s risk for type 2 diabetes and metabolic dysfunction-associated steatotic liver disease (MASLD)? The researchers are now analyzing those connections using data from the Teen-LABS study.