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Obesogens

Obesogens may interfere with body weight regulation

(Credit: Obesity Action Coalition)
The study also found that higher blood levels of PFASs were linked with lower resting metabolic rate or slower metabolism after weight loss

A class of chemicals used in many industrial and consumer products has been linked to greater weight gain after dieting, particularly among women, according to a study led by Harvard TH Chan School of Public Health. The chemicals - perfluoroalkyl substances (PFASs) – have previously been linked with cancer, hormone disruption, immune dysfunction, high cholesterol, as well as obesity.

The study also found that higher blood levels of PFASs - known as obesogens because they may upset body weight regulation - were linked with lower resting metabolic rate (RMR) or slower metabolism after weight loss. People with a lower RMR burn fewer calories during normal daily activities and may have to eat less to avoid becoming overweight.

 “Obesogens have been linked with excess weight gain and obesity in animal models, but human data has been sparse,” said senior author, Dr Qi Sun, assistant professor in the Department of Nutrition at Harvard Chan School. “Now, for the first time, our findings have revealed a novel pathway through which PFASs might interfere with human body weight regulation and thus contribute to the obesity epidemic.”

PFASs have been used for more than 60 years in products ranging from food wrappers to clothing to pots and pans, and studies have shown that they’ve contaminated drinking water near industrial sites, military bases, and wastewater treatment plants. These chemicals can accumulate in drinking water and food chains and persist for a long time in the body.

For the study, ‘Perfluoroalkyl Substances and Changes in Body Weight and Resting Metabolic Rate in Response to Weight-Loss Diets: A Prospective Study,’ published in PLOS Medicine, the researchers, with colleagues from Louisiana State University and Tulane University, analysed data from 621 overweight and obese participants in the Prevention of Obesity Using Novel Dietary Strategies (POUNDS LOST) clinical trial, which was conducted in the mid-2000s. The trial tested the effects of four heart-healthy diets on weight loss over a period of two years. Researchers looked at the possible connection between the amount of PFASs in participants’ blood as they entered the study and their weight loss or gain over time.

During the first six months of the trial, participants lost an average of 6.4 kg, but regained 2.7kg over the course of the following 18 months. Those who gained the most weight back also had the highest blood concentrations of PFASs, and the link was strongest among women. On average, women who had the highest PFAS blood levels (in the top third) regained 1.7-2.2kg more body weight than women in the lowest third.

In addition, the study found that higher blood concentrations of PFASs were significantly associated with lower resting metabolic rates.

“We typically think about PFASs in terms of rare health problems like cancer, but it appears they are also playing a role in obesity, a major health problem facing millions around the globe,” said study co-author, Dr Philippe Grandjean, adjunct professor of environmental health at Harvard Chan School. “The findings suggest that avoiding or reducing PFAS exposure may help people maintain a stable body weight after they successfully lose some weight, especially for women.”

Other Harvard Chan School authors of the study included lead author Gang Liu, Klodian Dhana, Jeremy Furtado, Geng Zong, Liming Liang, Lu Qi, and Brent Coull.

To access this paper, please click here

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