Kids' weight rises the longer mom works, study finds

It may not be what working moms want to hear, but a new study has found that the longer that a mother works outside the home, the more likely it is that her kids will become overweight.

The study, which is already generating plenty of controversy, appears in the journal Child Development. It found that the total number of years that children's mothers worked outside the home had a cumulative influence on their children's body mass index (BMI) – a key weight-to-height ratio used to measure obesity.

"We want to emphasize that this is not a maternal employment issue; this is a family balance issue," lead researcher Taryn Morrissey told CTV's Canada AM from Washington.

"This is not about maternal employment per se; this is about some other environmental factor or several factors."

Morrissey and fellow researchers from American University in Washington, Cornell University in New York State and the University of Chicago studied data on more than 900 children in 10 U.S. cities, focusing on kids in Grades 3, 5, and 6.

They found that for every five months or so that a mother was employed was linked to an increase in her child's BMI that was 10 per cent higher than other kids their age.

"For a child of average height, this is equivalent to a gain in weight of nearly one pound (half a kilogram) every five months above and beyond what would typically be gained as a child ages," the study authors said.

This "small but significant" increase over time can lead to an increased likelihood that the children will become overweight over time, they said.

The findings were strongest among children in 5th and 6th grades, with those kids being the most likely to gain weight when their mothers worked, compared with other children.

The researchers tried to account for the weight difference by looking at the children's physical activity, as well as their time spent watching TV and the time they spent on their own. But they found no differences in these factors between children with both parents working and those with just one parent working.

Though the researchers were unable to clearly explain the findings, "we have hunches on what may be behind this link," Morrissey said.

She explained that other studies have found that families in which both parents work tend to eat out more often, eat more fast food, and are more likely to skip breakfast.

The authors suggest that working parents have limited time for grocery shopping and food preparation and may rely more on outside food sources that tend to be high in fat and calories.

The authors speculate that the reason that 5th and 6th graders tend to put on more weight if both parents are working may be explained by the fact that they generally have more independence and less adult supervision over their time use and food choices than third graders, so having their mother working "precipitates poorer food choices and more sedentary activity," they wrote.

Morrissey says there are steps working parents can take to ensure their children eat properly, such as ensuring that there are always regular meal times and skipping the fast food when they can.

"I know that families are really time crunched so that is often hard but doing as much as you can could be one way to try to prevent this," she said.

Morrissey noted that with previous studies finding that the children of two working parents tend to sleep less, parents should also ensure their children are well-rested.

"We know that quantity and quality of children's sleep is really important to their BMI, so making sure that kids get the age-appropriate amount of sleep is another way [of ensuring their children's health]," Morrissey said.

Given that the majority of mothers in both the U.S. and Canada work outside the home, the authors say efforts need to be expanded to ensure the availability of affordable, readily accessible healthy foods, and to support and educate working parents about strategies for providing nutritious meals despite busy schedules.

Dr. Yoni Freedhoff, the medical director of the Bariatric Medical Institute in Ottawa, says he finds the study's findings interesting.

"I think what is really important here to notice is that this is a really complicated issue. I don't think many people would have thought that whether they were working or not would have a bearing on their children's weight. We need to stop simplifying obesity to say people are eating too much and moving too little; it is a complicated problem with a lot of variables," he told CTV News.

He says the study should make families reflect on what and how they're eating.

"I would not recommend that moms retire as a consequence of this study," he said. "I think that instead, people need to take a look at their homes, make sure that there is healthy food available in the homes, make sure that cooking is something that is still done."