Obesogens: These Chemicals May Be Keeping You Fat

Ruben Castaneda, Anna Medaris Miller

Invisible ingredients

If you've ever tried to lose weight, you may have tracked calories, read nutrition labels and cut down your portion sizes. But you probably didn't consider one factor increasingly implicated in the obesity epidemic: chemicals. One 2018 study in PLOS Medicine, for example, found that overweight and obese adults with higher concentrations of man-made chemicals known as PFASs in their blood regained weight more quickly after weight loss. PFASs are in everything from food packaging to household cleaners. The study was the first to suggest pollutants can interfere with people's weight-loss efforts, says one of its authors, Dr. Qi Sun, an associate professor in the Harvard T.H. Chan School of Public Health's department of nutrition.

Fat-promoting chemicals

The news was validating, but not surprising, to Bruce Blumberg, a professor in the departments of developmental and cell biology and pharmaceutical sciences at the University of California--Irvine, who coined the term "obesogen" in 2006 to describe invisible substances that encourage your body to gain or hold onto fat. "There are chemicals that can change the way our body handles calories," says Blumberg, whose research has shown that a single exposure to a small amount of an obesogen early in life can make mice obese later in life. Research by Sun and colleagues suggests something similar may be true in humans. While not easy, Sun says, "it is feasible to reduce your exposure." Here's where to start:

Your cupboard

Whether your aim is healthy eating or chemical exposure reduction, the best course of action is the same: Eat as many whole, unprocessed foods as possible, and limit your packaged food purchases, experts say. "That's got to be job No. 1 because then you control what's in the food," says Blumberg, whose book, "The Obesogen Effect," lists added and processed sugars, artificial sweeteners, monosodium glutamate (aka MSG) and other additives like artificial colors as "nutritional obesogens" to be avoided if and when you buy packaged foods. He notes that research published by the journal Cell Metabolism in May 2019 suggests that people who consumed a diet with ultra-processed foods ate 500 calories more per day than they did on a minimally processed regimen. In addition, a 2017 meta-analysis suggests that long-term use of artificial sweeteners, for one, may be linked to increased body mass index, though more research is needed.

Your restaurant meal

If clearing out your cupboard has left you hungry and headed out to eat, keep in mind you may be served an unwanted side of phthalates -- a group of hormone-disrupting chemicals found in plastics and many other products. The chemicals may be obesogenic; one German study, for instance, found that mice with a certain phthalate in their drinking water packed on pounds. Phthalates are prevalent in restaurant, fast food and cafeteria meals, research in the journal Environmental International suggests. Folks who ate at those establishments most, the researchers found, had phthalate levels nearly 35% higher than those people who prepared their own grocery store purchases. The worst offenders? Purchased burgers and sandwiches.

Your takeout containers

It's not just restaurant food itself that may be delivering diners' weight-gain-promoting chemicals; the grease-proof containers, paper wrappers and boxes many menu items are served in contain PFASs too, experts say. "Because they're both oil-repellent and water-repellent ... they're widely used in many consumer products," Sun says. In fact, the U.S. Food and Drug Administration banned some PFASs commonly found in pizza boxes in 2016. The linings of microwaveable popcorn bags are another common culprit too, Blumberg says. "They're all lined with chemicals one way or the other."

Your produce drawer

While all fruits and vegetables are nutritious whether they're organic, conventional, canned or frozen, not all produce is obesogen-free. Like Blumberg, Tracey Woodruff, a professor in the University of California--San Francisco School of Medicine and an author of the dining-out study, recommends shopping organic when possible. Since many pesticides are endocrine-disrupting, meaning they can mess up your hormones, they may have the potential to contribute to weight gain. When you can't buy organic, look to the Environmental Working Group's "dirty dozen" and "clean 15" lists to learn which conventional fruits and veggies are most and least contaminated. While strawberries are particularly "dirty," for instance, avocados are far fairer game. "An added bonus for eating fresh food is that you will reduce exposure to harmful chemicals that are present in processed and packaged food, like phthalates," Woodruff says. "Also, remember not to prepare your food in nonstick pots and pans, which may be contaminated with perfluorinated chemicals. I like to use what my grandmother used -- a cast-iron pan."

Your plastic ware

Your breakfast bar is wrapped in plastic, your lunch is packed in a reusable plastic container, your water is in a plastic bottle and your snacks are sealed in plastic baggies. While plastic is pretty much impossible to entirely avoid, every change -- be it drinking from a glass bottle instead of a plastic one or bringing your own bag on grocery trips -- can reduce your exposure to chemicals like bisphenol A. One study showed a BPA byproduct can lead cultured cells to become fat cells. "Plastic of all kinds leeches components into the food," says Blumberg, who suggests removing plastic from your life as much as possible.

Your receipts

Next time you're asked, "Do you need your receipt?" at the grocery store, consider saying "no" not just to avoid pocket clutter and environmental waste, but also to reduce your exposure to potentially obesogenic chemicals including BPA, which can be absorbed into your blood through the skin or even air when touching such receipts and other thermal papers, Blumberg writes in his book. Keep in mind, though, that the foods listed on that receipt contribute far more to your health and chemical exposure than the slip of paper itself. "There's no point in (avoiding these other exposures) if you don't take care of your diet," Blumberg says.

These chemicals may be keeping you fat:

-- Fat-promoting chemicals

-- Your cupboard

-- Your restaurant meal

-- Your takeout containers

-- Your produce drawer

-- Your plastic ware

-- Your receipts