Obesogen is a name we gave to chemicals that can inappropriately stimulate either the development of fat cells or the storage of more fat in pre-existing fat cells. This is a finding we first published in 2006, and it is starting to catch attention. We show that a class of chemicals called organotins are obesogens. Other labs have shown that Bisphenol-A and PFOA (a carboxylic acid used for such things as non-stick coating) are obesogens. There may be others. No one has really looked before. We encounter obesogens in a lot of different ways. They leach out of plastic food and beverage containers (things like plastic bottles that contain bottled water). So they enter our food supply.

In 2006 he fed pregnant mice tributyltin, a disinfectant and fungicide used in marine paints, plastics production, and other products, which enters the food chain in seafood and drinking water. "The offspring were born with more fat already stored, more fat cells, and became 5 to 20 percent fatter by adulthood," Blumberg says. Genetic tests revealed how that had happened. The tributyltin activated a receptor called PPAR gamma, which acts like a switch for cells' fate: in one position it allows cells to remain fibroblasts, in another it guides them to become fat cells… The effect was so strong and so reliable that Blumberg thought compounds that reprogram cells' fate like this deserved a name of their own: obesogens.

Obesity is communicated from parents to children through many potential Obesogens' — from the choices available at breakfast, the transport to school, the contents of the lunchbox, the weekend activities, the rules on eating sweets or the presence of TV sets in the bedroom.