Fair enough SKD, but there are the same percentage of households where both parents work now as in 1987 (
http://www.bls.gov/cps/wlf-table23-2006.pdf), and the number of obese kids has skyrocketed in that time.
Also, not all working parents are working for the same "reason". Sometimes both parents work because that's necessary to provide a roof over their heads and food on the table, and sometimes both parents work to have 2 new SUVs and a half million dollar house. Perhaps in the latter case, they could re-focus their priorities.