04/06/2012 04:06 pm ET Updated Jun 06, 2012

Are Environmental Chemicals Making Us Fat?

A small but growing number of researchers believe that environmental pollutants and industrial chemicals are to blame for the obesity epidemic. This, of course, bucks the conventional wisdom that our increasing girth is simply the result of eating too much and exercising too little. For those who have struggled unsuccessfully to lose weight according to the standard prescription ("eat less, move more"), this latest theory offers a sort of vindication -- if not a ready solution. But what's the evidence to support the idea that chemicals are the true cause of our ever-expanding waistlines?

It's not enough to say that the rise in obesity correlates to the increasing use of industrial chemicals. Although this may be true, the rise in obesity correlates to a lot of things. It also correlates to a dramatic increase in the sale of organic produce and other products. But there is more evidence.

Pesticides Make Rats Fat

Bruce Blumberg, a researcher at University of California, Irvine, researches the effects of chemicals that are widely used in plastics and pesticides. He's found that rats exposed to these chemicals have more and bigger fat cells than rats that are not -- even though both rats eat the same diet. Blumberg believes that the presence of these chemicals (he calls them "obesogens") in our environment could explain why we've gotten so much fatter.

This is a very interesting finding -- but it doesn't quite close the case. First of all, things don't always work in humans the way they do in lab rats. Secondly, these rats are being exposed to levels much higher than anything we encounter in our environment. While I think we should do whatever we can to reduce our exposure to industrial pollutants, it remains to be seen whether the amount of chemicals that the average citizen is exposed to is enough to affect our metabolism or fat cells -- and if so, how big that effect might be.

Why Are We Fat? A Simpler Explanation

Is there anything else that might explain the rise in obesity rates? Well, in 1970, the average American consumed about 2,200 calories a day, which happens to be the recommendation for an average-sized American with a healthy body weight. Today, the average American consumes about 2,700 calories per day. According to mainstream nutrition theory, eating an extra 500 calories a day would cause you to gain weight -- more or less a pound a week. Eventually, however, you'd stabilize at a weight of 30-40 pounds higher. That prediction lines up pretty closely with the change in average body weight over the last 40 years.

The idea that how much you weigh is simply a factor of how many calories you take in versus how many you burn is currently unpopular -- it's seen by many as overly simplistic. Then again, the principle of Occam's Razor states that the simplest explanation for any phenomenon is the most likely one.

Maybe Both Sides Are Right

Media coverage tends to cast the issue as a fight between experts who believe that calories don't matter and those who insist that they are all that matter. A recent article by Kristin Wartman in the Atlantic sets it up like this: "Researchers believe that [industrial chemicals] ... may be altering the way our bodies store fat and regulate our metabolism. But ... many scientists, nutritionists, and doctors are still firm believers in the energy balance model. A debate has ensued."

To me, it seems perfectly plausible that exposure to industrial chemicals could play some role in our metabolisms... But it's rather unlikely that our increased caloric intake plays no role. And, to be honest, despite how they are quoted in the press, I don't think the scientists on either side of this "debate" are seriously arguing that obesity has one and only one cause. The real debate is how big an impact the various factors might have -- and what we can reasonably do about them.

How to Reduce Your Exposure to Toxins

Whether or not you believe that industrial pollutants are making us fatter, I think there are plenty of other good reasons to avoid them. Unfortunately, it's not that easy. You can reduce your exposure by buying organic whenever possible, making sure that any plastic that comes into contact with your food or water is BPA-free, and using non-toxic chemicals in and around your home.

More tips on how to reduce chemical exposure: Which Foods Are Highest in Pesticides
How to Detoxify Your Body

But the sad truth is that industrial chemicals permeate our environment and it's virtually impossible to avoid them completely. Advocating for tighter regulations or bans on certain chemicals might be an even more effective way to reduce your exposure.

In the meantime, our inability to completely avoid industrial pollutants does not mean that we are all doomed to be obese. Whatever role these toxins may play, I think their impact is secondary. When it comes to the fight against flab, making smart choices about what and how much you eat is still your most powerful weapon. And fortunately, those are factors that you can control.

For more by Monica Reinagel, MS, RD, click here.

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