Day 80: Pesticides give you … obesity?

On the surface, obesity looks to be a self-inflicted wound. Too much food and not enough exercise, right?

Not so simple.

A new study in PLoS ONE adds heft to a link between pesticides and obesity that’s been emerging for the past several years. Soo Lim, of the Department of Internal Medicine at Seoul National University College in Korea, is lead author. Lim and colleagues exposed a group of lab mice to low levels of the common pesticide atrazine. Then, they divided the group: half the mice ate a fatty diet, and the other half ate normally.

The authors report that the pesticide decreased metabolism, increased body weight, and jacked insulin resistance even in mice eating the normal diet. A high-fat diet just made it worse.

Furthermore, atrazine decreased oxygen consumption and hindered basic aspects of cell signaling. 

“These results suggest that long-term exposure to the herbicide ATZ might contribute to the development of insulin resistance and obesity, particularly where a high-fat diet is prevalent,” Lim and her team report.

The authors point out that atrazine, also called ATZ, has been used heavily in this country since the early 1960s, “a time frame that corresponds to the beginning of the present obesity epidemic.” 

Furthermore, maps of atrazine use and obesity across the United States show “striking overlap,” the authors note. (I would argue that the proposed link doesn’t appear to explain everything.)

You can see a bigger version of the map in the study, by clicking the source link at the bottom of this post.

The authors acknowledge there is “scant information in the literature to indicate the level of human exposure to ATZ or similar herbicides.”

“Obviously, there is no direct evidence of ATZ accumulation in diabetic or obese human subjects,” they write. But some data has quantified significant exposure through diet.

“We believe that ATZ or its metabolites may be introduced to humans through air, water and and/or corn products as contaminants, and accumulate in tissues,” the authors continue:

One such pathway by which ATZ or its metabolites might be introduced into humans is through corn-derived foods (e.g., high fructose corn syrup or corn oil). Since corn syrup and fast foods served in the USA are suspected of causing an obesity epidemic, this seems a reasonable supposition. Recently, it was reported that of 160 food products purchased at a fast food restaurant throughout the USA, not a single item could be traced back to a non-corn source. This work also identified corn as the overwhelmingly predominant animal feed for the beef and chicken served at fast food restaurants.

Ew.

This isn’t the first time such a link has been alleged between synthetic chemicals and obesity. Two years ago, University of Missouri biologist Frederick vom Saal sounded the alarm about an endocrine-disrupting toxin commonly found in pesticides and plastics that can consign babies to a lifetime of risk for obesity. And in December, a pair of Japanese researchers published a study in BioScience implicating a common pollutant called Tributylti. Tributylti is used as an anti-fouling agent in paints for boats, as a wood and textile preservative, and as a pesticide on high-value food crops, among many other applications. The press release for that study is here.

Source: The new study, in PLoS ONE