By David Epstein / ProPublica
Everyone knows Americans are fat and getting fatter, and everyone thinks they know why: more eating and less moving.
But the “big two” factors may not be the whole story. Consider this: Animals have been getting fatter too. The National Pet Obesity Survey recently reported that more than 50 percent of cats and dogs — that’s more than 80 million pets — are overweight or obese. Pets have gotten so plump that there’s now a National Pet Obesity Awareness Day. (It was Wednesday.) Lap dogs and comatose cats aren’t alone in the fat animal kingdom. Animals in strictly controlled research laboratories that have enforced the same diet and lifestyle for decades are also ballooning.
In 2010, an international team of scientists published findings that two dozen animal populations — all cared for by or living near humans — had been rapidly fattening in recent decades. “Canaries in the Coal Mine,” they titled the paper, and the “canaries” most closely genetically related to humans — chimps — showed the most troubling trend. Between 1985 and 2005, the male and female chimps studied experienced 33.2 and 37.2 percent weight gains, respectively. Their odds of obesity increased more than 10-fold.
To be sure, some of the chimp obesity crisis may be caused by the big two. According to Joseph Kemnitz, director of the Wisconsin National Primate Research Center, animal welfare laws passed in recent decades have led caretakers to strive to make animals happier, often employing a method known to any parent of a toddler: plying them with sugary food. “All animals love to eat, and you can make them happy by giving them food,” Kemnitz said. “We have to be careful how much of that kind of enrichment we give them. They might be happier, but not healthier.”
And because they don’t have to forage for the food, non-human primates get less exercise. Orangutans, who Kemnitz says are rather indolent even in their native habitats in Borneo and Sumatra, have in captivity developed the physique of spreading batter.
Still, in “Canaries in the Coal Mine,” the scientists write that, more recently, the chimps studied were “living in highly controlled environments with nearly constant living conditions and diets,” so their continued fattening in stable circumstances was a surprise. The same goes for lab rats, which have been living and eating the same way for thirty years.
The potential causes of animal obesity are legion: ranging from increased rates of certain infections to stress from captivity. Antibiotics might increase obesity by killing off beneficial bacteria. “Some bacteria in our intestines are associated with weight gain,” Kemnitz said. “Others might provide a protective effect.”
But feral rats studied around Baltimore have gotten fatter, and they don’t suffer the stress of captivity, nor have they received antibiotics. Increasingly, scientists are turning their attention toward factors that humans and the wild and captive animals that live around them have in common: air, soil, and water, and the hormone-altering chemicals that pollute them.
Hormones are the body’s chemical messengers, released by a particular gland or organ but capable of affecting cells all over the body. While hormones such as testosterone and estrogen help make men masculine and women feminine, they and other hormones are involved in a vast array of functions. Altering or impeding hormones can cause systemic effects, such as weight gain.
More than a decade ago, Paula Baille-Hamilton, a visiting fellow at Stirling University in Scotland who studies toxicology and human metabolism, started perusing scientific literature for chemicals that might promote obesity. She turned up so many papers containing evidence of chemical-induced obesity in animals (often, she says, passed off by study authors as a fluke in their work) that it took her three years to organize evidence for the aptly titled 2002 review paper: “Chemical Toxins: A Hypothesis to Explain the Global Obesity Epidemic.” “I found evidence of chemicals that affect every aspect of our metabolism,” Baille-Hamilton said. Carbamates, which are used in insecticides and fungicides, can suppress the level of physical activity in mice. Phthalates are used to give flexibility to plastics and are found in a wide array of scented products, from perfume to shampoo. In people, they alter metabolism and have been found in higher concentrations in heavier men and women.
In men, phthalates interfere with the normal action of testosterone, an important hormone for maintaining healthy body composition. Phthalate exposure in males has been associated with a suite of traits symptomatic of low testosterone, from lower sperm count to greater heft. (Interference with testosterone may also explain why baby boys of mothers with higher phthalate levels have shorter anogenital distances, that is, the distance between the rectum and the scrotum. Call it what you want, fellas, but if you have a ruler handy and find that your AGD is shorter than two inches, you probably have a smaller penis volume and a markedly higher risk of infertility.)
Baille-Hamilton’s work highlights evidence that weight gain can be influenced by endocrine disruptors, chemicals that mimic and can interfere with the natural hormone system.
A variety of flame retardants have been implicated in endocrine disruption, and one chemical originally developed as a flame retardant — brominated vegetable oil, or BVO — is banned in Europe and Japan but is prevalent in citrusy soft drinks in the U.S. Earlier this year, Gatorade ditched BVO, but it’s still in Mountain Dew and other drinks made by Gatorade’s parent company, PepsiCo. (Many doctors would argue that for weight gain, the sugar in those drinks is the primary concern.) PepsiCo did not respond to a request for comment, but shortly after the Gatorade decision was made a company spokeswomansaid it was because “some consumers have a negative perception of BVO in Gatorade.”
And then there are the newly found zombie chemicals, which share a nasty habit — rising from the dead at night — with their eponymous horror flick villains. The anabolic steroid trenbolone acetate is used as a growth promoter in cattle in the U.S., and its endocrine disrupting metabolites — which wind up in agricultural run-off water — were thought to degrade quickly upon exposure to sunlight. Until last month, when researchers published results in Science showing that the metabolites reconstitute themselves in the dark.
Says Emily Dhurandhar, an obesity researcher at the University of Alabama-Birmingham: “Obesity really is more complex than couch potatoes and gluttons.”
bob dorn says
From time to time we read articles that seem designed to relieve us of the need for action to correct damaging lifestyles. They’re bad medicine. This one is a good example.
It’s a long stretch to connect the fattening up of feral rats in Baltimore to environmental chemicals. It’s simpler and more convincing to say that the garbage in Baltimore might be full of sugary, fatty food, as does garbage everywhere in the U.S. The author ought to have thought of that, especially because he spent the first six paragraphs presenting the idea that pet owners and zoos are keeping their animals happy “by plying them with sugary foods.”
Elsewhere, the author continues to pander to our weakness for fats and sugars by raising other causes that are really only potentials. “Antibiotics MIGHT increase obesity…” and “Altering or impeding hormones CAN cause systemic effects” he says. Where are the studies? What do the scientists conclude?
Okay, brominated vegetable oil (BVO) interferes with the endocrine system, which must be a shorthand way of saying that this disruption causes obesity because the author then leaps to the suggestion that Pepsi and Mountain Dew contain it. Both contain a pile of sugar in every bottle and can. Ever see how much of this stuff fat people are wheeling out of the supermarkets?
The jamming of fats and sugars into the maws of our pets and zoo animals is enough to make me figure that it’s the fats and sugars that are making humans fatter. That and a lack of exercise. Epstein seems to want to catch our eyes by admitting that indolence and gluttony are “the big two” causes our pets are fat, and then tries to sell some shaky and minor speculation that we’re not entirely to blame for our own blubber.
Doug Porter says
I disagree, Bob.
The cautionary tales woven into the story are neither “shaky” nor “minor speculation” and are backed by substantive research both in the US and Europe.
A close family member of mine has suffered through two decades of thyroid and hormonal related illnesses. She’s been through every kind of test and seen a platoon of doctors in several major research centers.
Ultimately what we have learned is that unknown substances have disrupted her body’s systems. We’re reduced to medicating to ease symptoms. (Been there, done that on the dozens of various diet and natural approaches) And that brings me to the point here.
Every major scientific body from the WHO to the EU to the FDA has participated in studies on the role endocrine disrupters. Everybody agrees that there is a problem; what they disagree about are the specifics. We still don’t know enough about the intricacies of receptors and the methods by which chemical messengers work.
What is clear is that the chemical industry’s approach to this issue strongly mirrors that taken by the tobacco industry on health issues and the oil companies on climate change. That alone should be a cause for concern.
I thought the article was clear about hedging its bets on specifics but also pointing the finger at mounting evidence that something very bad is going on here. I don’t deny that we all need more exercise and a better diet. But I have personal knowledge that for some people those remedies simply don’t work.
Tulane University: http://e.hormone.tulane.edu/learning/endocrine-disrupting-chemicals.html
A new reputable journal dedicated exclusively to Endocrine studies:
European Instituted for Health and Consumer Protection website:
European Food Safety Agency report:
World Health Organization summary, with many links:
The TEDX site with a comprehensive overview:
bob dorn says
I didn’t intend to suggest endocrine disturbance is not an enormous problem; I could even easily be persuaded it may cause some obesity. I just don’t think the author tried to explain the relationship between, specifically, obesity and industrial toxins. Without that effort on his part, I have to remain skeptical on the subject, Doug, and lay the cause to overindulgence and indolence. I do think the author in the main has implied, only implied, that industrial chemicals are causing more obesity than we’ve experienced before. I’m going off now to follow your links. I’m supposing my mind can be changed on this subject; it has been before, on other subjects.