Endocrine-disrupting environmental chemicals, including some found in everyday plastics and pesticides, may influence obesity. When fetuses are exposed to these chemicals, their gene function may be altered, causing a greater risk of obesity and disease.
An individual exposed to these chemicals as a fetus could eat the same thing and exercise the same amount as someone with a normal metabolic system, but be far more likely to become obese.
Researchers examined the effects of these chemicals, including bisphenol-A, on lab mice. They caused the mice to be born with abnormally low birth weights, and then gain abnormally large amounts of weight over a short period, more than doubling their body weight in just a week.
The mice were then obese throughout their lives. Similar effects have been observed in low birth weight children.