Since 1900, the energy requirements for daily life have decreased substantially with the advent of labor-saving devices and automobiles, yet American weights remained stable until the 1970s. Dr. Boyd A. Swinburn, an obesity researcher at Deakin University in Melbourne, Australia, and his co-authors in one Lancet paper call that decade the “tipping point.”
As more women entered the work force, the food industry, noting a growing new market, mass-produced convenience foods with palate appeal. The foods were rich in sugar, salt and fat, substances that humans are evolutionarily programmed to crave.
“Women were spending a lot less time on food preparation, but the industry figured out ways to make food more readily available for everybody,” Steven L. Gortmaker, a sociologist at the Harvard School of Public Health, said in an interview. “The industry made it easier for people to consume more calories throughout the day.”
As Dr. Swinburn and his co-authors wrote, “The 1970s saw a striking rise in the quantity of refined carbohydrates and fats in the U.S. food supply, which was paralleled by a sharp increase in the available calories and the onset of the obesity epidemic. Energy intake rose because of environmental push factors, i.e., increasingly available, cheap, tasty, highly promoted obesogenic foods.”
