On Wednesday, I reviewed a paper by John Cawley and Feng Liu about the mechanisms by which maternal employment can affect childhood obesity. It turns out that Cawley and Liu aren’t the only ones interested in this issue. A recent working paper by Fertig, Glomm and Tchernis investigates the same question.
The authors use time diaries from the Child Development Supplement to the PSID. They use two regressions to test their hypothesis. First, they regress BMI on the amount of time spent in various activities (e.g.: eating, watching TV, playing video games). The second regression measures how maternal employment impacts each one of these activities. In general, these regressions are estimated using OLS, but some activities are count variables (e.g.: number of meals in an average day) and the authors use a Poisson regression in these cases.
For the Poisson regression to be accurate, one must assume the mean and variance of the distribution must be the same. I would have preferred for the authors to use a negative binomial regression to increase flexibility, but I do not know whether this methodological alteration would change the results.
Some of the results of the paper are not surprising. For instance, maternal employment leads to more TV watching for the children and more TV watching leads to more childhood obesity.
Yet other results are interesting. Cawley and Liu found that working mothers cook fewer meals at home and that lead to more childhood obesity. Fertig and co-authors also found that working mothers cook fewer meals at home, but that the percentage of meals eaten at home did not affect childhood obesity in a statistically significant manner.
One of the major determinants of childhood obesity is the number of meals they eat. Missing breakfast and eating fewer meals, according to the authors, “may lead to higher concentrations of 24 hour insulin, which, in turn, can lead to increased fat deposition and higher body weight.” Children of working mothers eat fewer meals and having fewer meals significantly increases obesity.
Maybe breakfast is the most important meal of the day.
- Fertig A, Glomm G, Tchernis R, 2006. “The Connection between Maternal Employment and Childhood Obesity: Inspecting the Mechanisms” CAEPR Working Paper #2006-020.
Thanks to Scott Cunningham for sending me this working paper.