It’s no secret that when babies are exposed to harmful substances while in the womb it can have detrimental effects on their health later in life. This was the case with women in the 1950s who were given a drug called DES during pregnancy to prevent miscarriage that was later found to increase their daughters’ risk of developing cervical or vaginal cancer. Scientists are now taking a closer look at what substances may be present in pregnant women that could be impacting the later development of their children and causing them to be fat.

One explanation for the obesity puzzle that’s gaining credence is early-life exposure to traces of certain chemicals and pollutants in the environment –now commonly referred to as endocrine disruptors. These chemicals are so similar to human (and animal) hormones that they can block or disrupt the actions of regular hormones in both.

There is mounting evidence of a strong link between early exposure to some of these endocrine disruptors and the later development of obesity. Apparently these compounds act on genes in the developing fetus and newborn to turn more precursor cells into fat cells, which may pre-dispose babies and young children to becoming and staying fat. They can also alter metabolic rates, so that the body tends to hoard calories rather than burning them.

In one study conducted by Dr. Bruce Blumberg of the University of California, Irvine, pregnant mice were fed a substance called tributyltin –a disinfectant and fungicide used in marine paints and plastics production that enters the food chain through seafood and contaminates our water supply. Their offspring were born with more fat cells and fat already stored, and became 5 to 20 percent fatter by adulthood. The genetic tests revealed that the tributyltin activated a receptor, which acts like a switch, determining whether a cell remains a fibroblast (cells that make up the body’s connective tissue) or becomes an adipocyte (a fat cell).

The ability of these endocrine disruptors to re-program the fate of a cell and convert it to a fat cell is what led to the coining of a new phrase to describe them: Obesogens.

Not all endocrine disrupting substances are obesogens, but the biggest culprits so far are phthalates, bisphenol-A (also referred to as BPA), and some compounds used in stain repellants and non-stick cookware. Additional studies in Spain and Belgium have linked fetal exposure to pesticides and PCBs with childhood obesity.