According to the study, a child's weight increases by about one pound for each 5.3 months the mother works. Researchers aren't sure why. According to canada.com on Feb.7, 2011:
Perhaps one reason why the researchers cannot clearly explain the findings is that they have incorporated a huge bias into the very foundation of their study - gender. They looked for a correlation between absent mothers and fat children and found it, thereby focussing the problem on women exclusively.
(A disclaimer here - I can find only the media reports of the study, which are often skewed. Also, I would really like to know who funded this study.)
Reuters (June 2010) reported on an earlier study done in the UK and published in the American Journal of Epidemiology in which researchers looked at working mothers as one contributing factor amongst several which affect childhood obesity:
So the trend in mothers' employment over the past few decades may be one of the variables contributing to a general erosion in children's diets; the explosion in sugary junk foods on the market, food advertising aimed at kids, and the increasing availability of high- fat, high-sugar fare in schools are among the other factors that have been blamed.The researchers also considered socioeconomic factors.
I am not disputing the accuracy of the American study, nor am I making a comment on the possible advantages or disadvantages of working mothers.
The point is that a child's weight is influenced by several things, and the composition, quantity, and quality of a child's food, together with level of exercise, is not gendered.
North American kids have a weight problem. And there are many aspects to the problem: availability of junk food, advertising of junk food, lack of education about nutrition, absent parents, irresponsible parents, obese parents, tax subsidies to certain food producers, coercive advertising, not enough exercise...
Sure, working mothers have an effect, but how much easier it is to blame them than to fix the problem and possibly cut into somebody's profit margin, or spend the money really trying to educate people, or putting pressure on governments and companies to ensure the availability of good food, or trying to eradicate poverty.