Frederick vom Saal is a professor of biological sciences in the Endocrine Disrupters Group at the University of Missouri-Columbia's College of Arts and Science who discovered that obesity may not be all about caloric intake and energy output and that there could be other factors inducing obesity.

He found that being exposed to environmental chemicals found in everyday plastics and pesticides while in the mother’s womb might make a person more prone to obesity and related diseases later in life.

By performing tests on mice, professor Frederick vom Saal showed that endocrine-disrupting chemicals from the environment could change the functioning of a fetus’s genes, alter a baby’s metabolic system and predispose them to obesity. If two people ate the same amounts of the same food and exercised equally, the one who was exposed to these environmental substances would become obese while the one who hadn’t would not become obese.

One of the chemicals involved, called bisphenol-A, has been used on children’s toys, dental filling and for coating food cans. Vom Saal found that exactly this chemical as well as other made mice to be born at extremely low weights to gain abnormal weights in just 7 days after. These mice stayed obese their whole life-time.

Vom Saal said that we do inherit genes but how those genes develop during your very early life also plays an important role in your propensity for obesity and disease. Babies born with low weights have metabolisms programmed for starvation, which means that their body would keep the entire energy intake. The problem is that the children do not live in the starvation world but in the world of fast food.

Vom Saal believes that there are between 1,000 of the 55,000 human-made chemicals in the world that belong to this endocrine disrupting category. These chemicals are found in common products, from plastic bottles and containers to pesticides and electronics.
More research needs be done to determine which chemicals cause this effect.