Just what are “obesogens”?
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I first heard the word ‘obesogens’ two years ago from a colleague, who had been trolling the web in search of stories.
“They’re chemicals that make us fat,” she said.
“Come on – we’re fat because we eat too much and we don’t exercise enough.”
“Well there’s this guy called Blumberg…”
Bruce Blumberg coined the term ‘obesogens’ in 2005, after getting the results of a ground-breaking study of pregnant lab mice fed a marine pesticide called tributyltin.
Around 2001 he’d been looking for sex reversals in snails and flounder as a result of the pesticide. Much to his surprise, he discovered that it was also turning reproductive cells into fat cells. Then he came across a review by a Scottish doctor was suggesting a link between environmental chemicals like DDT, dioxins and organochlorines, and rising rates of obesity. Dr. Paula Baillie-Hamilton had discovered that researchers had been reporting pathological weight loss as a result of ingestion of these chemicals, but failed to highlight any weight gain they may have found. But in very low doses, they were definitely seeing weight gain.
Blumberg decided to launch a mouse study, using the same pesticide, the endocrine-disrupting tributyltin. He wanted to know if fetal exposure would lead to overweight baby mice.
“We found out that a single prenatal exposure to tributyltin at day 16 of development could cause mice to be born with more fat stored at birth and to become fatter later in life.”
Around the time Blumberg was searching for the hormone receptor that was causing the growth of fat cells in the frog’s testes, Retha Newbold, a government researcher in North Carolina specializing in the now banned drug D.E.S., was told by her lab technicians that she would need bigger cages because her mice were getting too fat for them. D.E.S., like tributyltin, is an endocrine disruptor. After reading Baillie-Hamilton’s review, she began designing her own study.
In Missouri, Fred Vom Saal, an expert on the health effects of bisphenol A (BPA), was also getting fat lab mice as a results of trace amounts of BPA. Not surprisingly, BPA is also an endocrine disruptor.
Obesity in Canada has doubled in less than thirty years. Every second adult in the western world is overweight. We have all presumed this is because of the widespread adoption of a western lifestyle full of fattening food and low levels of exercise. But some epidemiologists noted that even newborn babies were fatter than they used to be. As well, animals that live in proximity to people, like farm and lab animals, have become fatter since the 1950s. Was something programming us in the womb to be a little fatter than we should be?
Follow-up studies by Newbold and Vom Saal were positive. By 2007 there was enough evidence for the existence of obesogens that grant money for more studies began flowing from the National Institute of Environmental Health Sciences in North Carolina.
Retha Newbold has little doubt what is going on. “What we’re doing with these developmental exposures,” she said to me, “is that we’re programming people so that they will develop obesity later on in life and that’s something that’s going to be passed on to future generations. I think we have to really be concerned that our focus is on prevention.”