When Taryn W. Morrissey and her colleagues from Cornell University and the University of Chicago released their study on the relationship between childhood obesity and mothers’ work schedules, they were met with a torrent of international media interest and general anxiety. The findings based on data from 990 children in grades 3, 5, and 6 in 10 cities across the country suggested a relationship between children’s BMI and their mothers’ work lives that caused a stir. SPA’s assistant professor in public administration and policy shares the motivation behind the study, what the research means for policy makers, and what is yet to be discovered.  

What inspired you to look at the relationship between working moms and childhood body mass index (BMI)?

Over the past few decades, we've seen a tripling in the childhood obesity rate in the U.S., which has long-term health, economic, and social consequences for children as they grow older. My coauthors and I are interested in how family dynamics and factors are associated with child obesity. 

Several studies in this area had identified maternal employment as one factor associated with children's obesity, and we sought to uncover the reasons for this link. If we understand the environmental factors that explain the link between child body mass index (BMI) and maternal employment, we can help families and policymakers to promote healthy weight among children. This study extended previous research by identifying an additional factor, the total time mothers worked over the child's lifetime, as just one of the many factors at play in the current epidemic of childhood obesity. No one has found a single smoking gun as the cause of increased childhood obesity, and our study is no exception.

What were the study's main findings, and how large is the association between the total time moms work and their children's BMI?  

We found that the length of time mothers worked across their children's lifetimes is associated with a small but statistically significant increase in the BMI of their children (but not in the incidence of being overweight or obese). It is a small increase, about 1 pound over and above what you would expect for a child of average height at 3rd grade for each period a mother worked, which averaged between 5 and 6 months. 

This does not mean that a child whose mother worked continuously from birth through 6th grade would be 19 lbs. heavier than a child whose mother was not employed during those years, because the association is much smaller at younger ages and slightly larger at older ages, because of changes in BMI as children age. We don't have a specific number for the size of the association, but on average, the cumulative association between the total time moms work and an increase in their children's weight is around a few pounds for a child of average height.

What factors did you examine that might account for the link between maternal employment and children's BMI?  

Because we know that BMI increases result from increased caloric intake, decreased energy expenditure, or a combination of both, the total time moms work must be associated with their children's BMI through a factor that either increases food intake or decreases physical activity. We tested several potential factors that may account for this link. Children's physical activity predicted lower BMI, but maternal employment duration remained a separate, independent predictor of BMI. We tested the time children spent watching TV, which could displace physical activity or increase snacking. Like physical activity, this didn't explain the connection we found between maternal employment duration and BMI. That is, maternal employment duration remained an independent predictor of BMI. This may be due to the measure of TV time available in the data, which was either mother-reported or child self-reported, and may underestimate the actual time spent watching TV.

We also don't know the content of the TV programming. Watching programming with more junk food advertisements is linked with more snacking and increased caloric intake. We also tested maternal depression, the amount of time the child spent in structured activities, with parents, or without adult supervision, finding that none of these factors explain the link between the duration of maternal employment and children's BMI.

Our findings don't indicate that it is maternal employment per se that contributes to this increase. Rather, other environmental factors contribute to children's BMI appear to vary with the amount of time mothers spend at work; It's a reality that most mothers simply have to work, and often times long hours. If we can understand the underlying environmental factors that lead to the association we've found between maternal employment and BMI, then we can help inform policies that help working parents promote healthy weight among their children.

Your study did not identify the factor or factors that underlie the relationship between the total time mothers work over a child's lifetime and children's BMI. Why didn't you look at fathers' employment and the role it plays in children's BMI?         

Previous research provides some evidence that children's nutritional intake, mealtime routines, sleep patterns, or the quality of child care may play a role in the relationship between maternal employment and children's BMI.

Children's nutritional intake or eating patterns and routines have been identified as important in the relationship between maternal employment and children's BMI. Children in dual-earner families are more likely to skip breakfast than children with a parent at home. Working parents spend less time preparing meals at home and spend a greater proportion of their food budget on fast food or prepared foods than families with a non-employed parent. We know that fast food tends to be of poorer nutritional quality and has higher calories than home-cooked meals, and that skipping breakfast is associated with increased obesity. We also know that regular family mealtimes are associated with a lower likelihood of child obesity.

Unfortunately, we were not able to test the effect of fathers' employment duration, status, or schedule given the lack of variability in that the large majority fathers or mother's partners work full-time outside the home. That is, the large majority of fathers work and work full-time; there are few stay-at-home dads in our dataset. In addition, information on fathers' employment schedules (whether they worked day, evening, weekend, or variable shifts) was not asked in the dataset we used, so we could not look at what happens when parents' schedules overlap, or when they complement each other (e.g., moms work during the day, dads at night). I don't know of other studies that look at paternal employment, likely because also because of the lack of variability in fatherss' employment status. However, as more fathers take on greater child-rearing and household activities, we may be able to investigate this question in the future.  

Did the study take into account other family factors associated with children's BMI, like family income?  

Yes. We used statistical models that related within-child changes in maternal employment status and children's BMI, which control for all stable factors that differ between children, like race or ethnicity, gender, and mother's age or education at the child's birth. One important point to note is that this study, as well as all other studies in this area, we controlled for family income. Obviously, working moms contribute to family income, and higher family income is associated with improved child outcomes and lower child BMI, so this should be taken into account.  

Do the associations between maternal employment and child BMI vary by children's age?

Yes. There is some indication that this association is greater at 6th grade than at 3rd or 5th grades. At 6th grade, the association between the total time mothers worked and children's BMI was larger than at the younger ages. There was also an association between a mother's entry or re-entry into the workforce at 6th grade and a one-time increase in her child's likelihood of being overweight. Because we looked at within-child changes in maternal employment status and child BMI, this does not mean that children whose mothers work are more likely to be overweight than children whose mothers are not employed. This is an association between maternal employment stability and children's obesity, and we don't know why these moms were entering or re-entering the workforce at this time.  

What are some policy implications of the study? 

Public policies that enhance the availability of healthy food and nutrition information may help parents better balance work and family responsibilities. The cost of fruits and vegetables have increased over the past few decades, whereas the cost of prepared foods has decreased. Policies that enhance the availability of healthy foods at grocery stores, in terms of the affordability of fresh fruits and vegetables and the hours and geographic location of supermarkets, may help working families promote their children's nutrition. More information on preparing quick and easy but healthy meals may help working families prepare more meals at home, which tend to be healthier than eating out. In addition, policies that enhance the availability of affordable, high-quality child care programs with healthy foods and physical activities may be one way of preventing child obesity. Today more and more moms are working from home. 

Do you think rates of obesity would be similar or different for their kids at all (as opposed to moms who work outside the home)?

I think it would be very, very similar. So many factors contribute to child obesity, and the association that has been identified with maternal employment is a small one. The implication of this study is not for mothers to quit working. The large body of research indicates that maternal employment is not harmful for children's development; a few studies have identified small associations between maternal employment during infancy (9 months of age or younger) and slightly poorer child cognitive or social-emotional outcomes, but this, once again, is a small association. Other studies report no or positive effects of maternal employment on their children. One important point to note is that this study, as well as all other studies in this area, we controlled for family income. Obviously, working moms contribute to family income, and higher family income is associated with improved child outcomes and lower child BMI, so this should be taken into account. 

What is the takeaway message of this research?  

The bottom line is that this study highlights a work-family issue for all working parents, not a maternal employment issue. Our study is not a guilt-inducing finding; maternal employment per se does not lead to increased child BMI. Rather, the constraints working parents face while trying to negotiate work and family demands present the issue. If we can shed light on these constraints and the many factors that contribute to child BMI, we can help parents balance work and family demands and promote healthy weight among their children. These findings can be used to start a conversation about how society as a whole can better support working parents successfully balance work and family life.

What can families do to help promote a healthy weight and BMI among their children?

There are many resources with helpful tips for what families can do to promote child nutrition, healthy eating, sleep, and physical activity habits. A few are listed below. The National Heart, Lung, and Blood Institute's (National Institutes of Health) We Can! Campaign, The Centers for Disease Control and Prevention Healthy Youth Resources, and First Lady Michelle Obama's Let's Move Campaign.