More than 1 in 3 U.S. adults has obesity. Yet it is a relatively recent problem. The obesity rate only started skyrocketing in about 1979. Let's put that into perspective. If the 200,000-year history of Modern Man was the equivalent of one complete calendar year, with January 1 marking the emergence of Man, the U.S. obesity epidemic doesn't begin until roughly 10:23 p.m. on December 31.

How did we get so fat, so fast?

Anything that causes obesity is obesogenic. While researchers have rightly pointed to our increasingly obesogenic physical environment (e.g., the ubiquity of processed foods, etc.), what about our chemical environment? Could the chemicals around us be partly to blame for our expanding waistlines?

The chemical environment theory
Here's the theory: Hunger, satiety, and body fat are, at least in part, all regulated by hormones. Many chemicals that are virtually omnipresent in our environment today, were nonexistent 100 years ago. Some of these chemicals (endocrine disrupters) have been shown to impact normal hormonal functioning. Therefore, it stands to reason that chronic exposure to these chemicals could, either directly or indirectly, impact body weight. Recent research has increasingly found endocrine disrupters such as phthalates and bisphenol-A (BPA) to be obesogenic.

Phthalates are man-made chemicals designed to make plastics more flexible and are found in everyday products including cosmetics, fragrances, hand soap, shower curtains, and vinyl flooring.

Common phthalates include:

  • BBP (benzyl butyl phthalate)
  • DIDP (diisodecyl phthalate)
  • DINP (diisononyl phthalate)
  • DBP (dibutyl phthalate)
  • DNOP (di-n-octyl phthalate)
  • BBzP (benzyl butyl phthalate)
  • DEHP (di 2-ethylhexl phthalate)

People get exposed to phthalates and BPA in many ways (e.g., through the skin, ingestion, and inhalation, etc.). Endocrine disruptors aren't necessarily all bad, for all people, all the time (e.g., soy). However, chronic exposure to phthalates does have negative effects. In fact, California has banned the use of phthalates in toys.

The case against phthalates and BPA
While "correlation doesn't equal causation," the evidence against phthalates and BPA is mounting, and concerning.

A study published in Environmental Health Perspectives last month found that the more fast food you eat, the greater your blood levels of certain phthalates and BPA (potentially from indirect exposure from the food wrappers), so it may not just be the calories from fast food that's making us fat.

High levels of phthalates in the body are associated with Type II diabetes and abdominal obesity, particularly in men. In mice, exposure to certain phthalates promotes body fat, and exposure to BPA promotes the creation of new fat cells and makes it harder to lose fat. Chronic exposure to these endocrine disrupters may even trigger human genetic changes in utero ("epigenetics").

The bottom line
Body weight is complex and multi-determined. Diet, portion sizes, processed foods, and a sedentary lifestyle are all clearly implicated in the obesity epidemic, but there's mounting evidence that chronic exposure to certain chemicals may also play a role.

To date, no study has experimentally tested whether reducing exposure to phthalates and BPA leads to weight loss or improved health — the science isn't there yet. That said, there's certainly no evidence that chronic exposure to these chemicals has any health benefit whatsoever. Let common sense prevail. Consider limiting your exposure, especially if you are of childbearing age.

Easy and inexpensive lifestyle changes to reduce your exposure

  1. Ditch the plastic containers. For storing and microwaving leftovers, consider using glass containers instead. Trade in any hard-plastic personal water bottles containing BPA, for ones made of metal or glass, as BPA may slowly "leach" over time. (Plastics with BPA will have a "7" recycling code on the bottom.)
  2. Ditch the BPA-lined cans. Even a single exposure to BPA (drinking soymilk from a BPA-coated can) has been shown to raise blood pressure. Trader Joe's and Eden Organics are good sources of BPA-free canned goods.
  3. Ditch the non-stick pans. Non-stick pans commonly contain polyfluoroalkyl chemicals. A growing body of research suggests that we are accumulating these chemicals in our bodies (98 percent of the population has detectable levels of polyfluoroalkyl chemicals in their blood). Children with greater in-utero exposure to these chemicals (through their mothers' blood supply) had more body fat by the age of eight. Safer alternative: stick with pans that stick.
  4. Limit fast food. Cut the calories, cut the chemicals.
  5. There's an app for that. Free smartphone apps let you scan product barcodes for information on tens of thousands of personal care products. Knowledge is power. Check out apps by Think Dirty© and Environmental Working Group (EWG), including Food Scores for packaged foods.

Stacey C. Cahn, PhDis associate professor of clinical psychology at the Philadelphia College of Osteopathic Medicine (PCOM). Dr. Cahn specializes in obesity, weight stigma, eating disorders, and cognitive-behavioral therapy. 

Michael P. McGuinness, PhD is professor of anatomy at Philadelphia College of Osteopathic Medicine (PCOM). Dr. McGuinness conducts research on phytoestrogens and their role in inflammation. 

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