Researchers tracked the post-diet results of 381 Europeans who lost a minimum of 8% of their original weight after two months of dieting and found those who had the highest levels of polyfluoroalkyl substances, or PFAS, in their blood gained back the most weight.

By Douglas Fischer | Environmental Health News |4/23/2023

Frustrated that the pounds keep flooding back after losing weight on a diet?

Per-and polyfluoroalkyl substances, or PFAS, pervasive environmental contaminants known as “forever chemicals,” could play a role, according to a new study published April 17 in the journal Obesity.

The study took a novel approach to a frustrating conundrum many adults have experienced at some point: Pounds that slowly creep back on after successful weight loss and despite faithful adherence to a healthier diet.

Researchers tracked the post-diet results of 381 Europeans who had lost a minimum of 8% of their original weight after two months of dieting and tested their blood for PFAS, a family of chemicals used to make everything from firefighting foam to nonstick products and that have been linked to obesity.

‘The obesity pandemic’

All participants stayed on a specific diet for at least 26 weeks after the initial weight loss.

Those who gained the most weight back had the highest levels of PFAS chemicals, researchers found. Study participants ranking in the top third of PFAS exposure regained an average of 10 pounds more than those in the bottom third of the exposure curve.

And perhaps even more alarming, higher background PFAS exposures had an even greater effect on weight gain than the diet, researchers found.

“The results suggest that PFOA and PFHxS may cause weight gain among people with obesity in weight loss programs,” the researchers concluded. “These pollutants deserve attention in public health efforts to control the obesity pandemic.”

Obesity has several causes. But researchers have long been puzzled at how people on the same diets — say, low carbohydrate — react so differently, suggesting some other factors are at play.

Hormone hijackers

The new research suggests that PFAS and other mostly invisible environmental contaminants could play a role.

“PFAS exposures add to our risk of obesity,” said Philippe Grandjean, a study author and a research professor at the University of Rhode Island. “It’s not just a matter of lacking physical activity and eating a poor diet.”

Grandjean and colleagues previously examined weight loss and weight gain in people from Massachusetts and Louisiana and found PFAS exposure was linked to gaining weight back after initial loss via dieting.

The researchers pointed out that PFAS have been shown to interfere with thyroid hormones, which are crucial for maintaining proper metabolism.

Americans have more PFAS

There are a number of confounding factors, however, the authors note in the new study.

For starters, we are awash in obesogens — chemicals that can cause the human (and animal) body to produce, store and burn fat tissue differently than it normally would. Everything from BPA to air pollution affects how our body processes, stores and reacts to calories.

The study sample was fairly homogenous, consisting of adults with obesity in Europe. It’s an area worth studying, the researchers suggest.

“Given the sizable increases in weight regain linked to PFAS exposures,” they wrote, “future dietary trials may wisely consider blood concentrations of these contaminants to obtain more precise results.”

Originally published by Environmental Health News.

Douglas Fischer is the executive director of Environmental Health News.