Tuesday, February 08, 2011

How It Is Done: Working Mothers, Guilt and Childhood Obesity

So I see this:
Are your kids chunky? It could be your fault, mom.
A new study published in the journal Child Development suggests that working mothers are partly to blame for their children’s weight problems.
The study, conducted by researchers at American University, Cornell and the University of Chicago, found a small positive correlation between mothers’ long workdays and their children’s body mass index (BMI).

We find that maternal employment has a cumulative influence on children’s BMI that, over time, could lead to an increase in the likelihood that a child is overweight or obese,” write the study’s authors. Nonstandard employment – that is, work schedules that include nights and weekends – was particularly associated with obesity.
The article then goes on summarizing another study about food in infancy and concludes with this:
So, moms, if you’re going to bottle-feed your child, don’t be too eager to crack open the baby food jars. And try not to work long hours, especially when your kid is in sixth grade.
Did all you working mothers go and rend your clothes and scatter ashes on your head? Did you atone in any other way? Did you get so angry that the breath out of your noses steams now?

Well, not quite so fast. Another popularization of the same study explains a very central problem with the study:
But dietician, Kary Woodruff, from Intermountain’s Orthopedic Specialty Hospital says don't heap on the guilt quiet so fast. “There are some points in there that are important to address, but it’s more multi-factorial than it presents."

For example, she says the study failed to take in to account the socio-economic background of the children.
Woodruff then goes on discussing something which really does not matter in view of this omission. Because of statistical reasons, ultimately.

To see why that is the case, notice that the study didn't control for the incomes of the families. This means that any correlation between poverty and obesity was just lurking somewhere in the background, hiding behind the variables which the study did look at.

What might be correlated with low incomes in a study like that? Hmm. Perhaps long working hours? Working weekends and nights to make more money than one otherwise might? Here is an example:
On a recent visit to Children's Hospital, 38-year-old Rachel (who, like many parents at this and other weight-loss clinics, prefers to use first names only with outsiders in order to protect her child's identity) listened to the changes she'd have to make in her 4-year-old son's diet and seemed a little daunted. "I'm still trying to process it all," she said a few days later. But Rachel's child is more fortunate than many of Ludwig's patients. The family lives in Brookline--in fact, right next to a Whole Foods store--so buying the healthy staples of a new and better diet wouldn't be that difficult. (Weaning her son off the snack food Pirate's Booty, she admitted, might be another story.) But not everyone is so fortunate, like a patient who visits soon after, an 11-year-old African-American girl. Her father works days, and her mother works nights; trying to find the time and budget to search out and prepare healthier food was clearly going to be harder for this family. "It's not impossible, but it's absolutely tougher for the family from the inner city where the parents are working two jobs," says Ludwig. "These are the trenches in the war against obesity."

I recommend reading that piece right after the first one I linked to, just to notice how different the flavors are.

To return to the topic, the work variable probably picks up some of the correlation between poverty and childhood obesity. It will do this even if the mother's working hours have nothing to do with childhood obesity as such, because that variable correlates with an absent variable which is known to be strongly correlated with early obesity.

Whether those working hours have a more direct impact or not cannot be analyzed when income levels are not controlled for. Ideally, one would like to compare identical situations except for changes in the one variable of interest, such as two genetically identical families with equal incomes, equal cultures, equal access to food in stores, with the only difference being in the working hours of the mother. When that cannot be done (which is always), the next best alternative is to try to take into account all other variables known to be linked to obesity. Given that poverty is one of the most important ones of those, the failure to control for incomes in this study makes the results meaningless.

I'm not sure if I have made the point clearly enough yet. A study which does not control for income in looking at obesity is like a study which looks at the correlation between warm clothing and winter sports without controlling for the local weather, and then attributes the prevalence of warm clothing to the practice of winter sports.

But whatever the demerits of the study, that popularization really is utterly loathsome. Loathsome! Note that working fathers are not mentioned. Fathers are not mentioned. And the recommendations for women, or rather the scolding: Try not to work so much!

I write about these kinds of crappy studies because they are worms which drill through the skins of women and fester deep inside us. We are not worthy! We are responsible! Nobody else is to blame! We must walk on our hands through life and not fall! I don't write about them because I somehow think that women are perfect, for example, but to show how this thing is done. It is non-stop, really.

And in this case it is probably attacking women who are already under stress because of poverty, because of having to work two jobs and because of living in an area without stores which stock nutritional food.