Childhood obesity rates have tripled since the early 1970s. Television, junk food, and fast food are all reasons. A recent study from the Chicago Fed highlights the role of working mothers in this problem. When the mother works, the child watches more TV, eats more junk food, and has fewer good meals at home, thereby becoming heavier. A causal impact is found, however, only for families in the top quarter of income distribution. Could hired nannies bear some part of the blame? The authors also note that schools have a financial incentive to encourage children to eat meals that are not very good for them (an argument for more school choice I might add), click here for more on that topic.