Weight Gain in Response to Environmental Toxins

Background: Though it has been hypothesized that fetal exposure to endocrine disrupting chemicals may increase obesity risk, empirical data are limited, and it is uncertain how early in life any effects may begin.

Objectives: To explore whether prenatal exposure to several organochlorine compounds (OCs) is associated with rapid growth in the first six months and body mass index (BMI) later in infancy.

Methods: Data come from the INMA (Infancia y Medio-Ambiente) Child and Environment birth cohort in Spain which recruited 657 women in early pregnancy. Rapid growth during the first 6 months was defined as a change in weight-for-age z-scores >0.67, and elevated BMI at 14 months as a z-score ≥ the 85th percentile. Generalized linear models were used to estimate the risk of rapid growth or elevated BMI associated with dichlorodiphenyldichloro-ethylene (DDE), hexachlorobenzene (HCB), beta-hexachlorohexane (bHCH), and polychlorinated biphenyls (PCBs) in 1st trimester maternal serum.

Results: After multivariable adjustment including other OCs, DDE exposure above the 1st quartile was associated with a two times increased risk of rapid growth among children of normal weight (BMI <25 kg/m2), but not overweight, mothers. DDE was also associated with elevated BMI at 14 months (relative risk per unit increase in logDDE 1.50, 95% confidence interval 1.11-2.03). Other OCs were not associated with rapid growth or elevated BMI after adjustment.

Conclusions: This study found prenatal DDE exposure to be associated with rapid weight gain in the first six months and elevated BMI later in infancy, among infants of normal weight mothers. More research exploring the potential role of chemical exposures in early onset obesity is needed.

From press release:

Babies whose mothers had relatively high levels of the chemical DDE in their blood were more likely to both grow rapidly during their first 6 months and to have a high body mass index (BMI) by 14 months, according to a team of scientists based in Barcelona, Spain. DDE, an endocrine disruptor, is a by-product of the pesticide DDT.

Published online October 5 ahead of print in the peer-reviewed journal Environmental Health Perspectives (EHP), the study examined data collected between 2004 and 2006 on a representative sample of 518 Spanish women in their first trimester of pregnancy. Among babies whose mothers were normal weight pre-pregnancy, those babies whose mothers had DDE levels in the top 75 percent of exposure were twice as likely to grow rapidly during their first 6 months as babies whose mothers had the lowest DDE levels. Infants in the top 50 percent of exposure were three times more likely to have high BMI scores at 14 months. The researchers did not observe an association between DDE and weight for babies of mothers who were overweight before pregnancy.

Two other human studies have shown an association between prenatal DDE exposure and obesity later in life. "However, this analysis suggests, to our knowledge for the first time, that fetal DDE exposure may promote rapid growth starting in the immediate postnatal period," report lead author and epidemiologist Michelle A. Mendez, of the Centre for Research in Environmental Epidemiology, and her colleagues. Laboratory studies have suggested that "exposure to chemicals with endocrine-disrupting properties might promote shifts in appetite regulation, but may also promote obesity through metabolic changes," says Mendez.

Only 14 percent of all the children had a BMI exceeding the 85th percentile, but rapid growers of both normal-weight and overweight mothers were five times more likely than other babies to have a high BMI at 14 months. Other studies have shown that infants who grow rapidly also tend to have higher levels of body fat. More than 40 studies have associated rapid weight gain in the first few months of life with obesity and metabolic disorders later in life, the team writes.

The team tested the mothers' blood serum for other organochlorine compounds with endocrine-disrupting properties, including polychlorinated biphenyls (PCBs), but these chemicals showed no association with early weight gain. The researchers controlled for other factors in rapid growth and high BMI, such as parents' height and weight, duration of breastfeeding, and whether the mother smoked. The team is continuing to study the children, who are now 4 years old.

"Most of the exposure to organochlorine compounds is thought to come from the diet," says Mendez. Foods including meats, fish, dairy products, and fruits and vegetables are potential sources of exposure to DDE and similar compounds. "These chemicals persist in the environment as they are highly resistant to degradation," Mendez says.