Regaining Weight? Blame Take-Out Foods, and Possibly the Packaging

With Qi Sun, MD, ScD, and J. Michael Gonzalez-Campoy, MD, PhD

Want to keep off the weight you just lost? Steering clear of those fast food burgers, fries, pizza, even Chinese food in those cool white boxes, may be a really good idea. It seems it's not only what's in those wrappers and packaging that matters.

Learning about the harmful health effects of environmental chemicals started with bisphenol A (BPA) in plastics, such as water bottles and the lining of cans. The issue of man-made chemicals is back, this time with a tongue-twisting name—perfluoroalkyl and polyfluoroalkyl substances (or PFAS).

Takeout wrappers and fast food containers contain chemicals that may lead to weight gain.

Even the Centers for Disease Control and Prevention has had this group of man-made substances on their radar for some time even though their effect on humans has not been well understood.1

Regular exposure to PFAS may contribute to weight regain, report experts from Harvard who studied the problem with funding from the National Institute of Environmental Health Sciences.2

Food-Packaging, Non-Stick Pans Could Be the Cause of Weight Gain

The authors found that certain food-related items (and some other household products) contain environmental chemicals or compounds that may lead to weight gain. 

To be safe, you’ll want to back away from:

  • non-stick cooking pan
  • fast food wrappers
  • carryout containers (ie, pizza boxes)
  • microwave popcorn bags
  • maybe even your carpet

"Our study demonstrates that those chemicals at the higher levels [in the blood] were associated with faster weight regain after dieting," says Qi Sun, MD, ScD, assistant professor of nutrition at the Harvard T.H. Chan School of Public Health and a senior author of the study,1 which was published in PLOS Medicine.

“Weight regain is a universal issue among those trying to get to and then maintain a healthy weight,” Dr. Sun tells EndocrineWeb. "For individuals who want to lose weight, it's not that hard, through diet and increasing physical activity;" he says, "however, it's really, really hard, almost impossible, to maintain the lost weight.”  

Eating takeout meals regularly doubles your risk of gaining weight: both the ingredients from these highly processed, high-calorie foods, and now their takeout wrappers and containers, offer even more reason to cook your own meals, or find healthier meals out.

Study Examines the Health Effects of the Environmental Toxin: PFAS

While the potential effects of PFAS on weight regain in animals has been studied, Dr. Sun says he believes his research is the first to look at the harmful effects of PFAS and weight regain in people.1

For this two-year study,2 the Harvard researchers followed 621 men and women, average age 51 years, who were enrolled in the trial known as POUNDS Lost (Preventing Overweight Using Novel Dietary Strategies).3  Dr. Sun and his colleagues found that most of the weight loss occurred in the first six months, followed by gradual weight regain from six months until the end of the study.2

At the study start, the average body mass index, or BMI, was over 32, which puts these individuals into the obese category, meaning their health is at greatest risk for conditions like heart disease and diabetes.2 A woman who is 5'8" tall and weighs 211 pounds has a BMI of 32.1, for instance.

The researchers measured blood levels of the PFAS at the beginning of the study. They also looked at changes in body weight, resting metabolic rate (RMR), and other metabolic factors over the two years that they followed these patients.

A Closer Look at the Link Between PFAS and Your Weight

During the first six months of the study, the weight loss period, people lost an average of 14 pounds. For the next 18 months, they regained an average of about six pounds.

Dr. Sun’s team noted that the blood levels of PFAS did not affect weight loss but did seem to have an impact on weight regain.2

“The higher the blood levels of PFAS after the end of weight loss period, the more weight people regained,” Dr. Sun says. Women and those with higher blood levels of PFAS regained the most weight.  In particular, women in the group with the highest PFAS levels gained back about four to five pounds more than those who had the lowest amount of PFAS in their blood.

Of course, going back to old, unhealthy eating habits could have contributed to weight regain. However, the researchers took into account how often the men and women reported craving French fries, hamburgers, and donuts at the study start and found the results largely unchanged. They also measured how many study sessions the men and women attended during the study, which reflects how well they were following the diet recommended for weight loss.

Understanding Why PFAS May Affect Weight Regain

Higher levels of PFAS in the blood were also linked with a lower resting metabolic rate (RMR), or a slower metabolism, Dr. Sun says, so those individuals with the most PFAS in their blood burned fewer calories.2

As to why women were more vulnerable to weight regain after exposure to PFAS, the researchers say the reason is still unclear, but there is some evidence to suggest that the chemicals may interfere with estrogen metabolism, perhaps making women more vulnerable to the weight-regain.2

One limitation of the study, the researchers admit, is that the PFAS levels were taken only at the start of the study. However, the chemicals are known to stay in the body a very long time.3

Where Are PFAS Commonly Hiding? 

It's not easy to avoid PFAS, Dr. Sun says. ''They are basically everywhere,'' that popular foods are found, he says, so "it’s very hard to completely avoid them."

However, you can reduce your exposure.

Be aware that PFAS are likely to be in common take-out food packaging, such as carryout pizza boxes and fast food wrappings. Of course, it wouldn’t hurt to cut down on those foods inside the packaging, too.  In addition to food wrappers, Dr. Sun says, “some waterproof clothing has PFAS as does some nonstick cookware. Some carpets are treated with PFAS.”

If you handle these products, wash your hands after touching these items, he says.

As to how much weight regain to blame on PFAS and how much should be argued that the weight gain was really from what you're eating inside that wrapper? That's something Dr. Sun can't say for sure.

What's In the Wrapper Matters At Least As Much

"The higher PFA levels may simply reflect the volume of food eaten, a possibility that the researchers also suggest," says, says J. Michael Gonzalez-Campoy, MD, PhD, FACE, medical director of the Minnesota Center for Obesity, Metabolism, and Endocrinology and an Endocrine Web editorial board member.

"So the levels [of PFASs] may be a marker of the quantity of food ingested, rather than a cause of weight gain," says Dr. Gonzalez-Campoy.

If that turns out to be the case, he says, ''Weight regain would reflect the amount of [fast] food ingested as opposed to a chemical effect from exposure to environmental compounds directly."

The bottom line: There are plenty of reasons to avoid eating fast food if you are trying to improve your health, including putting an effort into keeping lost weight off.

"The primary limitation [of the research] is that this is just one study," Dr. Sun says, so more research is needed to have a better understanding of how PFAS effect not only weight regain but peoples' health in general.

Neither Dr. Sun nor Dr. Gonzalez-Campoy have any financial conflicts of interest.



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