Obesity stems primarily from the overconsumption of food paired with insufficient exercise. But this elementary formula cannot explain how quickly the obesity epidemic has spread globally in the past several decades nor why more than one third of adults in the U.S. are now obese. Many researchers believe that a more complex mix of environmental exposures, lifestyle, genetics and the microbiome’s makeup help explain that phenomenon. And a growing body of work suggests that exposure to certain chemicals—found in nature as well as industry—may play an essential role by driving the body to produce and store surplus fat in its tissues. Evidence of that cause-and-effect relationship in humans is still limited, but in laboratory animals and in petri dishes data linking the chemicals to problematic weight gain are mounting.
