Obesogens are industrial chemical compounds found in our food and drugs that can alter body physiology and metabolic processes, which cause an individual to be predisposed to gain weight.
A professor at the University of CA, Irvine, discovered that when pregnant mice were exposed to tributyltin (TBT), an organotin, it predisposed their offspring to be heavier and get fatter even when they consumed a normal diet.
Human exposure to TBT is rare, but it has been found in human blood, milk, and liver samples.
However, this is not the only obesogen identified.
In 2012 about twenty different chemicals had been identified as obesogens by the National Institute of Environmental Health Sciences (NIEHS).
Some examples include chemical pesticides such as atrazine and DDE (a DDT breakdown product), diabetes drugs such as Avandia (rosiglitazone), as well as chemical compounds found in our foods today like soy phytoestrogen genistein 28 and monosodium glutamate (MSG).
Other identified obesogens include common endocrine disruptors such as bisphenol A (BPA), phthalates, and plasticizers found in PVC, air fresheners, as well as laundry and personal care products being used daily by many individuals today.
You can read more about obesogens here.