Study links chemicals in ‘BPA-free’ plastics to obesity in kids

Animal studies have linked obesity and other health problems with exposure to bisphenol A (BPA). That’s a common ingredient of many clear, hard plastics and the resins that line food cans. Concerns over BPA health impacts led manufacturers to start phasing out the chemical in products that make contact with foods and drinks. Now a study in children and teens suggests that even some BPA substitutes may foster weight gain.

Those substitutes — BPS (bisphenol S) and BPF (bisphenol F) — are now used as a lining in some aluminum food cans. They’re also found in the paper used to print cash-register receipts.

Melanie Jacobson works in New York City at the New York University School of Medicine. Her team’s new study finds that overweight kids tend to have higher levels of BPS and BPF in their bodies than do normal-weight kids. That would suggest that like BPA, these chemicals are obesogens (Oh-BE-suh-genz).

The group described its findings on July 25 in the Journal of the Endocrine Society. 

Some pollutants act like hormones

Hormones control many of the body’s activities. At least in animals, BPA can mimic estrogens, a type of hormone. In fact, animal studies had shown BPA could cause harm by interfering with the body’s natural hormones. The new data suggest some BPA substitutes also may be hormone mimics.

“It’s not surprising,” Bruce Blumberg says of the new findings. Previous research had linked BPA to obesity in both kids and adults. A cell biologist, Blumberg studies obesogens at the University of California in Irvine. He notes that a chemical’s structure, or shape, determines how it acts. And the chemical structures of both BPS and BPF, he notes, closely resemble that of BPA.

Exposure to obesogens “make us more likely to get fat than we otherwise would,” says Blumberg. Studies in rodents, he notes, show that BPA makes fat cells larger. That can encourage the body to store more food energy as fat. 

Linking chemicals and obesity

BPS and BPF have been studied far less than BPA has, notes Jacobson. For its new study, her team tapped into data from a national survey. It’s part of ongoing research to track the health and nutrition of children and adults across the United States. 

Jacobson’s team focused on data for 1,831 people. All were between the ages of 6 and 19. The measured data included each person’s weight, height and distance around the waist. People who are considered overweight have a higher weight and waist circumference than will others of their height.

The researchers used these data to compare each person’s body size. A normal body size for a 19-year-old girl is very different from that of a typical 6-year-old boy. So the researchers used a special calculation to adjust for age and sex. It “puts everyone on the same playing field,” explains Jacobson. 

Her team then compared each kid’s body size to the amount of bisphenols in their urine. BPA turned up in the urine of nearly every kid and teen (97.5 percent). Roughly 88 percent of them also had BPS. About 55 percent had detectable BPF.

Young people with higher levels of BPS in their urine were 16 percent more likely to be obese than were kids with lower levels. And kids with higher levels of BPF were 29 percent more likely to have abdominal obesity than were those with lower levels. Abdominal obesity is a high ratio of waist circumference to height.

The researchers found no link between BPA and obesity in the new data. 

Cutting exposure

“Our findings suggest that these newer chemicals also may be a factor in child obesity,” says Jacobson. What the findings don’t mean, however, is that these chemicals are making kids fat. The study shows a correlation — or link — between two things: chemicals and obesity. That’s different from saying one caused the other. Indeed, Jacobson says, “We don’t know whether the chemicals caused the obesity.”

The national survey data provided a snapshot of kids’ body sizes and chemical exposures from a single point in time. The researchers have no way of knowing which happened first — the chemical exposure or the obesity. Future studies could look to see whether bisphenol exposures lead to weight changes over time.

Scientists know that “a good diet and getting lots of exercise still are the most important things kids can do to maintain a healthy weight,” Jacobson says. Owing to her study’s new findings, she says kids may want to cut their exposures to BPS and BPF.

How? Avoid touching store receipts and eat fewer foods that come in cans, suggests Blumberg.

“Don’t microwave plastic food containers or put them in the dishwasher,” adds Jacobson. “When heated, [any bisphenols in them] are more likely to leach out into food and drink.”