Do environmental triggers play a role in causing the growing epidemic of obesity in the United States over the past 150 years?

"Obesity has risen steadily in the United States over the past 150 years, with a marked uptick in recent decades. In the United States today more than 35% of adults3 and nearly 17% of children aged 2–19 years are obese. Obesity plagues people not just in the United States but worldwide, including, increasingly, developing countries. Even animals -- pets, laboratory animals, and urban rats -- have experienced increases in average body weight over the past several decades, trends not necessarily explained by diet and exercise. In the words of Robert H. Lustig, a professor of clinical pediatrics at the University of California, San Francisco, '[E]ven those at the lower end of the BMI [body mass index] curve are gaining weight. Whatever is happening is happening to everyone, suggesting an environmental trigger.'"

Wendee Holtcamp reports for Environmental Health Perspectives February 1, 2012. [2]