How Long Moms Work Linked To Slight Increase In Kids' Weight

Researchers have found a link between the total amount of time mothers have worked in their child's lifetime and an increase in that child's body mass index, or BMI. Other factors — including the amount of TV the kids watched or the time of day moms worked — didn't explain the link.

So does that mean Mom should stay at home and not work? Not at all, says Taryn Morrissey, a developmental psychologist at American University and lead author of the study appearing in the journal Child Development.

For one thing, the difference was small, Morrissey says. For every five months or so a mother was employed while her child was growing up, a kid of average height would gain about a pound more than otherwise expected.

"Even if mothers were to quit the labor force tomorrow, obviously that would not solve the childhood obesity epidemic," Morrissey tells Shots. "It's not even clear that it would reduce it."

It's just reality that in most families both parents work, Morrissey says. According to the Bureau of Labor Statistics, 47 percent of moms were in the labor force in 1975. By 2008, that number rose to 71 percent.

In the past eight years, there's been more interest in how maternal employment relates to children's weight, Morrissey says. But she says that hers was the first study to look at total duration of employment during a child's lifetime as a factor.

In the paper, Morrissey and her colleagues used data from the Study of Early Child Care and Youth Development, a study initiated by the National Institute of Child Health and Human Development that tracked about 1,000 babies until age 15. The researchers looked at kids in 3rd, 5th and 6th grades, and they found that the difference was more pronounced in the older grades.

One finding that surprised Morrissey: TV time didn't factor into why mothers' employment was associated with higher BMIs in children. But she suspects moms and their kids weren't always reporting the entire amount of time the kids spent in front of the screen.

Susan Wenner Jackson, who blogged about this research in Working Moms Against Guilt, wrote that she doesn't like "being pegged with another societal problem (child obesity) because women need and want to work." Jackson also questioned why there wasn't more research on the impact in dads' working.

But Morrissey says there's not a lot of variability in fathers' employment. "They tend to be employed full time and pretty continuously, whereas that's not the case for mothers," Morrissey says. She also says the data set she used didn't collect information on fathers' work schedules.

Morrissey emphasized that this study should not make working mothers feel guilty.

"The problem is not maternal employment or working moms. It's the constraints that working families feel," Morrissey says, adding that two of the study co-authors are working moms with young kids.

Morrissey suggests that nutrition may play a role in the disparities. If families are pressed for time in general, Morrissey says, they probably have a hard time getting to the grocery store.

"Families in which most parents work tend to spend a lower proportion of their food budget on fruits and vegetables and spend a higher proportion on fast food and eating out, which we know has more calories," Morrissey says.

Morrissey says it's important that families have access to healthy choices — like fresh fruits and vegetables — in conveniently located supermarkets with hours conducive to working families.