What we were trying to find is what has changed in our environment that has led to obesity, study leader Edward Archer, a researcher at the University of South Carolina, told the New York Daily News.
What changed, he said, is that more women went to work at sedentary jobs and fewer engaged in physical activity like housework.
Obesity rates have been increasing steadily in past decades. In 2004, 32 percent of Americans were obese, compared to 13 percent in the 1960s, according to research from the Johns Hopkins Bloomberg School of Public Health.
For Archer's study, researchers looked at the time and amount of energy women expended on household management over a 45-year span.
Non-working women spent 33.1 hours per week on housework in the 1960s, compared to 16.5 hours in 2010. Working women spent 17.1 hours on housework in the 1960s, compared to 10.4 in 2010.
By 2010, women were devoting 25 percent more time to screen-based media use watching TV or on the computer.
The study is published in the science journal PLOS One.