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Organochlorines and obesity

29th January 2004

Researchers are increasingly concerned that environmental contaminants that affect hormone function in humans, including the oestrogen-like activity shown by organochlorines such as DDT, may be increasing our risk of excess body weight. A call for research proposals on links between endocrine-disruptors and obesity has been issued by the US National Institutes of Health.

The possible links have been recognised for several years, with research in the 1980s showing that one of the more widely used organocholorine pesticides, lindane, caused a significant increase in food intake and weight gain when administered to experimental animals. In humans, the levels of organochlorines in blood plasma are generally higher in people with higher body mass.

A possible explanation for a role in obesity is that the contaminants - soluble in fat and resistant to degradation - are dealt with in the body by storing them in fatty tissue, with extra fatty tissue created to reduce the concentration of the chemicals. In this sense, obesity may thus be a physiological adaptation to increasing exposure to toxic chemicals.

The result would be high levels organochlorines stored in body fat. It has been observed that when obese people are put on a weight reduction diets their circulating levels of organochlorines rise rapidly, as fatty cells shrink and release the chemicals, thus raising the risk of thyroid and autoimmune dysfunction and cancer.

In the call for further research, the National Institutes for Health is looking at early (in utero and neonatal) implications, the role of contaminants in influencing the function of fat cells, the interaction with genetic susceptibility to environmental agents as well as wider aspects of obesity in society.

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