The Downside of Weight Loss

Weight Loss May Release Pollutants Into Bloodstream, Researchers Say

Reviewed by Louise Chang, MD on September 07, 2010
From the WebMD Archives

Sept. 7, 2010 -- There may actually be an unhealthy downside to losing weight.

A new study finds that blood levels of substances known as persistent organic pollutants were higher in people who had lost weight compared to people who maintained or gained weight.

Persistent organic pollutants (POPs) are compounds created by humans in industrial processes and have been linked to a wide range of illnesses, including type 2 diabetes, cancer, dementia, and heart disease. The study appears in the International Journal of Obesity.

Persistent organic pollutants are stored in fat tissues in the body. But when the amount of fat is decreased -- as through weight loss -- they may be released into the bloodstream, where they may enter vital organs, such as the heart and brain.

The Study

In the study, researchers compared levels of seven common persistent organic pollutants in 1,099 adults who participated in a national health study in 1999-2002.

They found levels of POPs were significantly higher in adults who had experienced more weight loss. This effect was slightly higher in people who had maintained their weight loss for 10 years or more, compared with people who had sustained it for only one year.

Researchers say the findings may help explain why some studies have suggested, though not proven, that the risk of heart disease, dementia, or death may sometimes increase after weight loss.

However, it's still unclear whether this release of the persistent organic pollutants associated with weight loss or pre-existing obesity-related illnesses are responsible for this increase in risk. Further study will be needed to determine whether this release of persistent organic pollutants is responsible for any negative health effects following weight loss.

Show Sources


Lim, J. International Journal of Obesity, Sept. 7, 2010; online edition.

News release, Nature Journals.

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