DDT (dichlorodiphenyltrichloroethane), cadmium, and lead (Heindel and vom Saal, 2009; Newbold et al., 2008). Pollutants that act as endocrine disruptors include agents that are known to alter metabolism in experimental settings and may have analogous effects in adult humans, although there is no direct evidence of effects on infants or children. In one study of participants in the National Health and Nutrition Examination Survey, evidence was found linking levels of phthalates in blood to waist circumference and levels of insulin resistance in adults (Stahlhut et al., 2007). An analogous study in the National Health and Nutrition Examination Survey of polyfluoroalkyls did not find an association of blood levels with body mass index (BMI) or insulin resistance (Nelson et al., 2010).
In 2006, a paper published in Nature reported that microbial populations in the gut differ between obese and lean people, and that when obese people lost weight, the state of their microflora reverted back to that observed in a lean person, suggesting that obesity may have a microbial component (Turnbaugh et al., 2006). In a more recent study, Turnbaugh showed that the microbiota in the human gut can be transferred successfully to germ-free mice; that in germ-free mice transplanted with human fecal microbiota, a high-fat, high-sugar diet durably changes the transplanted microbiome; and that this diet-altered microbiome promotes obesity (Turnbaugh et al., 2009).
The chemicals of concern have a range of endocrine effects and are therefore of health concern independently of whether they influence obesity in children in particular. Regulation needs to take into account the full array of health concerns and target the most sensitive endpoints as the limiting factor in defining acceptable exposure levels. Reducing human exposure to these agents would have no known detrimental effects on health.
Enhanced efforts are warranted to determine whether such agents make a contribution to the marked changes seen in the occurrence of childhood obesity. Such efforts include further mechanistic research, as well as observational studies, to determine whether such exposures during gestation and early childhood are related to increased weight and elevated risk of obesity.
Heindel, J. J., and F. S. vom Saal. 2009. Role of nutrition and environmental endocrine disrupting chemicals during the perinatal period on the aetiology of obesity. Molecular and Cellular Endocrinology 304(1-2):90-96.