Boston, MA - A class of chemicals used in many industrial and consumer products was linked with greater weight gain after dieting, particularly among women, according to a study led by Harvard T.H. Chan School of Public Health. The chemicals--perfluoroalkyl substances (PFASs)--have been linked with cancer, hormone disruption, immune dysfunction, high cholesterol, and 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. Metabolism refers to the chemical processes in the body that convert energy from food, commonly known as "burning calories." People with a lower RMR, or slower metabolism, burn fewer calories during normal daily activities and may have to eat less to avoid becoming overweight.
The study will be published online February 13, 2018 in PLOS Medicine and will be available here: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002502
"Obesogens have been linked with excess weight gain and obesity in animal models, but human data has been sparse. 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," said senior author Qi Sun, assistant professor in the Department of Nutrition at Harvard Chan School.
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.
The researchers, with colleagues from Louisiana State University and Tulane University, analyzed 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 kilograms (kg), but regained 2.7 kg 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 1.7-2.2 kg 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 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.
Funding for the study came from NIEHS grants ES022981, ES021372, and ES027706. The POUNDS LOST trial was funded by NHLBI grant HL073286 and the General Clinical Research Center grant RR02635.
"Perfluoroalkyl Substances and Changes in Body Weight and Resting Metabolic Rate in Response to Weight-Loss Diets: A Prospective Study," Gang Liu, Klodian Dhana, Jeremy D. Furtado, Jennifer Rood, Geng Zong, Liming Liang, Lu Qi, George A. Bray, Lilian DeJonge, Brent Coull, Philippe Grandjean, Qi Sun, PLOS Medicine, online February 13, 2018, doi: 10.1371/journal.pmed.1002502
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Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people's lives--not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America's oldest professional training program in public health.