• Posted August 15, 2025

'Forever' Chemicals Might Hamper Weight Loss In Teens

“Forever” PFAS chemicals might hamper a teenager’s ability to drop excess weight, even if they’ve undergone weight-loss surgery, a new study says.

Teens with high blood levels of per- and polyfluoroalkyl substances (PFAS) were more likely to regain weight lost after bariatric surgery, researchers reported Aug. 14 in the journal Obesity.

“Our study shows a clear association between PFAS exposure and weight-related outcomes in bariatric surgery for adolescents,” lead researcher Brittney Baumert said in a news release. She’s a postdoctoral research fellow in population and public health sciences at the Keck School of Medicine of USC.

PFAS are called “forever chemicals” because they combine carbon and fluorine molecules, one of the strongest chemical bonds possible. This makes PFAS removal and breakdown very difficult.

PFAS compounds have been used in consumer products since the 1940s, including fire extinguishing foam, nonstick cookware, stain-resistant furniture, waterproof clothing and food wrappers, researchers said.

Previous studies have shown that PFAS chemicals disrupt hormones in the human body, potentially affecting metabolism and weight gain, researchers said in background notes.

“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,” Baumert said.

For the study, researchers tracked 186 teenagers who underwent bariatric surgery between 2007 and 2012.

Blood samples were taken before surgery and tested for seven types of PFAS, and the participants were tracked for up to five years after surgery for weight, body mass index (BMI) and waist size. (BMI is an estimate of body fat based on height and weight.)

Results showed that teens with higher PFAS blood levels before surgery regained more weight and had greater increases in waist circumference than those with lower levels.

The strongest links between the chemicals and excess weight were observed in a class of PFAS known as sulfonic acids, which includes perfluoroctaansulfonaten (PFOS) and perfluoroheptanesulfonic acid (PFHpS), researchers said.

For example, teenagers with the highest levels of PFOS regained about 47 pounds on average within five years of their surgery, compared with about 36 pounds for those with the lowest exposure levels, results showed.

And teens with highest PFHpS exposure regained an average 4.3% of their body weight per year following surgery, compared with 2.7% per year in the lowest exposure group.

These results add to mounting evidence that PFAS need stronger regulation, researchers said. This particularly applies to public water supplies, which are the greatest source of PFAS exposure in the U.S.

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

Researchers next plan to explore whether PFAS exposure might affect the impact of other weight-loss methods, such as GLP-1 drugs like Ozempic and Zepbound.

They also want to investigate whether PFAS chemicals increase risk of metabolic conditions like type 2 diabetes or fatty liver disease.

However, they noted the current study is observational and cannot draw a direct cause-and-effect link between PFAS and weight gain.

More information

The Environmental Working Group has more on PFAS chemicals.

SOURCE: Keck School of Medicine of USC, news release, Aug. 14, 2025