A controversial new study suggests the expansion of women’s waistlines over the past 45 years is at least partly due to the shift in traditional gender roles, with more women taking sedentary jobs outside the home and cutting back on housework and physically demanding domestic chores.
 

The study, published in the Public Library of Science journal PLOS One, is based on an analysis of “time-use diaries” tracking the daily activities of thousands of American women between 1965 and 2010.
 

Researchers from the Arnold School of Public Health at the University of South Carolina in Columbia who examined the diaries found most women were physically active at home in the 1960s — devoting an average of nearly 26 hours a week cleaning, cooking, and doing laundry. But by 2010, women spent about half that time — just over 13 hours per week — on household chores. Over the same period, sedentary activities at home — such as watching TV — and work increased dramatically.

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“One of the most dominant factors in the decrement of [housework] over time appears to be the change in women’s social roles,” the researchers concluded. “Early in the 20^th century, women allocated the vast majority of their time to unpaid [household] activities. Beginning in the 1950s, women began to divide their time between unpaid [housework] activities and paid employment. From 1950 to 2000, women’s full-time employment increased from 34 percent to 60 percent and the full-time employment of mothers with children increased from 19 to 57 percent.”
 

The USC researchers noted that transition led to “a dramatic decrease” in the time women spent on domestic chores and child care.
 

“This shift from more active activities such as [housework] to more sedentary occupational activities has an obvious impact of energy expenditure and health,” they noted. “These results suggest that the decrement in [housework] may have contributed to the increasing prevalence of obesity in women during the last five decades.”
 

For the study, lead researcher Edward Archer and colleagues reviewed information contained in the American Heritage Time Use Study, an extensive archive of reports thousands of women provided on how they spent their time around the house and at work.

Archer assessed how many hours the women worked or performed household chores, and calculated the calories they burned while performing job- and home-related tasks. The results indicated women burned far more calories at home in 1965 than in 2010, with working women employed outside the home burning about 360 fewer calories every day in 2010 than in 1965.
 

The findings echo a 2011 study of U.S. Bureau of Labor Statistics that found more Americans are sitting down on the job than 50 years ago, with physical activity at work virtually disappearing for most employees, who spend a large part of their time at a computer or talking on the phone.
 

The study found the average American worker burns 150 fewer calories daily at work than their parents, which may be a key role in the nation’s obesity crisis.
 

The USC researchers were clear to note that they aren’t advocating a return to outmoded gender roles or that more time should be spent by women, or men, doing housework. But the findings suggest Americans should spend less time sitting in front of a TV or computer screen and more time engaged in active pursuits — at home and at work.