Popular belief blames fast food like McDonald’s and Burger King, movies and popcorn, and the increasingly sedentary lifestyle of North America for rapidly raising rates of obesity. However, this view problematically simplifies the causes of obesity, and overlooks an extremely important segment of the population who don’t eat junk food, do not particularly enjoy exercise, and do not have a choice but to be sedentary: babies. According to a 2006 study by the scientists at the Harvard School of Public Health, the prevalence of obesity in infants under six months of age has risen 73 percent since 1980. That’s massive, and it can’t be explained by popular belief.

This statistic poses a huge problem to notions of obesity. It can not be explained in terms of couch potatofication and fast food. “Since they’re eating only formula or breast milk, and never exactly got a lot of exercise, the obvious explanations don’t work for babies. You have to look beyond the obvious,” says endocrinologist Robert Lustig of the University of California, San Francisco. The search beyond the obvious has led scientists to an interesting find: trace chemicals in the environment especially in food which may have adverse effects on developing babies, both inside and outside of the womb. These chemicals, when exposed to developing fetuses and newborns, can turn more precursor cells into adipocytes (fat cells), which stay with you for life, and alter metabolic rates, causing the body to hoard calories rather than burning them off. Environmental chemicals affect a large part of the obese population, especially those under fifty according to the National Institute of Environmental Health Science (NIEHS), and their effects during development may account for some of the frustration associated with an individual’s inability to lose weight.

The first spark of the idea that chemicals can cause weight gain came in an obscure paper published in 2002 by Paula Baillie-Hamilton of Stirling University in Scotland. This paper was published in the Journal of Alternative and Complementary Medicine, and noted a curious correlation between a rise in the use of chemicals like pesticides and plasticizers and obesity rates during the previous forty years. Most scientists took this link to be poppycock, because one could just as easily make the link between increasing obesity rates and the popularity of glam metal, which also took off in the good old 1980s. A few, however, did find the link to be an interesting one, and set off to figure out if it had any substance.

A team of Japanese scientists, for instance, discovered that bisphenol A, a plastic present in things such as baby bottles, causes certain precursor cells to become fat cells, and stimulates the proliferation of already existing fat cells. Upon hearing of this discovery, Jerrold Heindel of the NIEHS wrote: “The fact that an environmental chemical has the potential to stimulate growth of ‘preadipocytes’ has enormous implications.” That is to say, if this were to happen in living animals as it does in petri dishes in a laboratory, the result would be an animal with a tendency to become obese.

Another scientist that worked to show the proof of the link between obesity and environmental chemicals is Bruce Blumberg of the University of California, Irvine. In a 2006 study, he fed a common disinfectant and fungicide, called tributyltin, to pregnant mice. The offspring were born with a 5 to 20 per cent higher chance of becoming obese. These were such significant results that Blumberg decided to give a name to the chemicals that have such an effect on the body: obesogens.

Developing babies who are exposed to obesogens become programmed to produce more fat cells. The more fat cells you have, the more places there are for fat to be stored, and, if you are particularly efficient at burning calories (meaning there is more fat leftover for the body to store), then the leftover ones will remain in your fat cells and cause you to gain more fat cells. Moreover: those with more fat cells, and who are more efficient at burning fat, tend to feel more hungry more of the time. Blumberg explains this cycle, saying ,“One of the messages of the obesogens research is that prenatal exposure can reprogram metabolism so that you are predisposed to become fat.”

Traces of obesogens are found in the bodies of almost every American, so why aren’t all Americans predisposed to gaining fat cells? According to Blumberg, even the slightest changes to dosage and timing of exposure are crucial to the “fate” of cells. Even in genetically identical mice, he says, the reactions to obesogens were varied.

Obesogens are all around and pervade almost all elements of our lives. But, more research must be done regarding obesogens before conclusions can be drawn. One thing can be said for certain: the relationship we have with our physical environment is not one-sided. Just as we can the environment, the environment can have an equally powerful impact on us.