Feb. 4, 2011 -- The more years a mother works during her children's growing-up years, the more likely the children's weight is to rise, according to a new study.
The findings echo some previous findings but also extend them, according to researcher Taryn Morrissey, PhD, assistant professor in public administration and policy at American University.
''Whereas many previous studies have examined intensity of maternal employment in terms of her work hours, we extend this line of work by showing an association between intensity of maternal employment over the child's lifetime -- that is, cumulative exposure to maternal employment as the child grows older -- and her child's BMI [body mass index]," Morrissey writes.
Bottom line: The longer a mom's employment -- whether she's toiling at a regular 9-to-5 job or works irregular hours -- the more likely her child is to gain more weight than is healthy.
"This is not a reason for moms to feel guilty," Morrissey tells WebMD. ''It’s not maternal employment per se that's the issue. It's an underlying environmental factor that leads to this association."
What that factor (or factors) is has yet to be uncovered, she says.
The study is published in the journal Child Development.
Working Mothers and Weight Gain in Kids
Morrissey and her team evaluated data on 990 children who were enrolled in the Study of Early Child Care and Youth Development, sponsored by the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The children lived in 10 different cities across the country.
The researchers checked data about mothers' employment and kids' BMI when the children were in grades three, five, and six. The researchers looked at whether the mothers worked, whether they worked traditional schedules or not, and the length of the employment. They didn't look at how many hours were worked, Morrissey says, so there's no way to give a threshold of how many hours is linked to increasing weight in kids.
What they did find it that the total number of years that the mothers were working had a small but cumulative effect on the child's BMI.
How small? For every 5.3-month period the mother was employed, the child had a slight increase in BMI over and above what would be expected with normal weight gain with age.
"For a child of average height," Morrissey writes, "this is equivalent to a gain in weight of nearly 1 pound every five months above and beyond what would typically be gained as a child ages."
The association was strongest when the children were in fifth and six grade compared to third grade, perhaps because at that age children may make more food choices on their own.
Over time, the slight increases can tip the child into being overweight.
Little Time to Prepare Dinner
When the researchers looked at factors affecting why the kids gain weight, they didn't find a link, surprisingly, between changes in physical activity, the time spent in supervised activity, or TV watching time.
The time of day the mothers worked -- whether their hours were traditional or not -- did not explain the association either.
The researchers speculate working parents may have little time to grocery shop and to prepare healthy food.
More than 70% of U.S. mothers with young children work, so the effect of working on children's weight is far-reaching.
The new findings echo and in some ways repeat those of Patricia M. Anderson, PhD, professor of economics at Dartmouth College, who has published on the topic.
"I think mostly, this study confirms what the past literature has shown, but using a different sample of children than has been used in the past," Anderson tells WebMD.
"What continues to be lacking in this growing literature is a good explanation for the mechanism by which this maternal employment effect operates," she tells WebMD.
With little known about the why, what's a working parent to do? "I think I would focus on food," Anderson says. "Fast food doesn't necessarily have to be higher calorie. Take advantage of the nutrition information that many restaurants and supermarkets have available."
"When making the quick choice, still focus on making the good choice," she says. If you only have time for a trip through the drive-through, she says, order the small hamburger with fruit and milk, not the big burger and fries with soda.
''Additionally," she says, "parents could try to ensure that the child get more chances for physical activity to counteract the increase in prepared foods."
"A family meal [at home] once a week has been linked with lower obesity," Morrissey tells WebMD.
Working mothers can also be sure their kids get enough sleep, as lack of sleep has been linked with higher BMIs. Other studies show children of working mothers tend to skip breakfast, so feeding them breakfast before work and school may help reduce weight gain, too, she says.